7). 3 1/7 * (-4) - 1.8 : (-0.1) + 20/21 : 1 2/3

1. Convert mixed numbers and decimals to fractions: 22/7 * (-4) - 18/10 : (-1/10) + 20/21 : 5/3.

2. Perform multiplication and divisions: -88/7 - 18/10 * (-10) + 20/21 * 3/5 = -88/7 + 18 + 4/7.

3. Combine terms: (-88/7 + 4/7) + 18 = -84/7 + 18 = -12 + 18 = 6.

Final Answer: 6