Why is Jan so mean to me? If Jan 1 ______ (not be) so mean to me, I 2 ______ (want) to invite her to my party. The problem is, she's so popular. If she 3 ______ (not have) so many friends, nobody 4 ______ (care) if she was at my party or not. I have to invite her. If I 5 ______ (invite) Jan to my party, nobody 6 ______ (come) to it. Maybe I shouldn't have a party. But if I 7 ______ (not have) a party, I 8 ______ (not get) any presents and I want presents! Why are birthdays always so much trouble? If it 9 ______ (not be) my birthday next week, my life 10 ______ (not be) so complicated. If I 11 ______ (know) what to do, I 12 ______ (do) it. But I don't!

Solution:

• 1. The sentence structure "If Jan __ (not be) so mean..." suggests a conditional clause. Given the context of what might happen, this is likely a second conditional, implying a hypothetical or unlikely situation. The past tense of 'be' for 'Jan' (third person singular) is 'was'. However, for hypothetical situations in the second conditional, 'were' is often used for all persons, though 'was' is also acceptable in informal English. Considering the directness of the question and the typical structure taught, 'was' is a strong candidate.
• 2. "If Jan was so mean to me, I __ (want) to invite her..." This part of the sentence needs a verb that describes the consequence of Jan being mean. If Jan *is* mean, the speaker might *not want* to invite her. However, the sentence structure implies a hypothetical situation where if Jan *weren't* mean, the speaker *would want* to invite her. The second conditional requires the past tense in the 'if' clause and 'would' + base verb in the main clause. So, 'would want' fits.
• 3. "The problem is, she's so popular. If she __ (not have) so many friends..." This is another conditional. If she *didn't have* so many friends, perhaps people *would care* if she was at the party. This points to the second conditional again, requiring the past tense of 'have', which is 'had'.
• 4. "...nobody __ (care) if she was at my party or not." Continuing the second conditional from point 3, the main clause requires 'would' + base verb. So, 'would care'.
• 5. "I have to invite her. If I __ (invite) Jan to my party..." This presents a scenario about inviting Jan. The structure "If I __ (invite)... nobody __ (come) to it" suggests that inviting her would lead to no one coming. This is a consequence of an action. The use of 'nobody __ (come) to it' suggests a hypothetical outcome, fitting the second conditional structure. So, the past tense of 'invite' is 'invited'.
• 6. "...nobody __ (come) to it." Following the second conditional structure from point 5, the main clause should be 'would' + base verb. So, 'would come'.
• 7. "Maybe I shouldn't have a party. But if I __ (not have) a party..." This is a hypothetical situation about not having a party. The second conditional is implied. The past tense of 'have' is 'had'.
• 8. "...I __ (not get) any presents..." This is the consequence of not having a party, within the second conditional framework. Thus, 'would not get'.
• 9. "If it __ (not be) my birthday next week..." This is a statement about a future event that might or might not happen. The phrasing "If it __ (not be)... my life __ (not be) so complicated" suggests a hypothetical condition. This is a standard second conditional structure. The past tense of 'be' for 'it' is 'was' (or 'were').
• 10. "...my life __ (not be) so complicated." This is the consequence of the condition in point 9, within the second conditional. Thus, 'would not be'.
• 11. "If I __ (know) what to do..." This is a hypothetical situation about knowing what to do. This fits the second conditional structure. The past tense of 'know' is 'knew'.
• 12. "...I __ (do) it." This is the consequence of knowing what to do, within the second conditional. Thus, 'would do'.

Completed sentences:

1. Why is Jan so mean to me? If Jan was (or were) so mean to me, I would want to invite her to my party.
2. The problem is, she's so popular. If she didn't have so many friends, nobody would care if she was at my party or not.
3. I have to invite her. If I invited Jan to my party, nobody would come to it.
4. Maybe I shouldn't have a party. But if I didn't have a party, I would not get any presents and I want presents!
5. Why are birthdays always so much trouble? If it was (or were) not my birthday next week, my life would not be so complicated.
6. If I knew what to do, I would do it. But I don't!