№3. Вычислите: 1) - 14 +9; 2) 28 + (-5); 3)-21-16; 4)-19-(-81); 5) - 2,5-1,9; 6) \frac{3}{16}+\frac{5}{12}; 7)-\frac{10}{11}-(-\frac{10}{11}); 8)1\frac{2}{9}+(-\frac{2}{27}).

Ответ: 1) -5; 2) 23; 3) -37; 4) 62; 5) -4,4; 6) \frac{29}{48}; 7) 0; 8) \frac{31}{27}

Решение:

1. -14 + 9 = -5
2. 28 + (-5) = 28 - 5 = 23
3. -21 - 16 = -37
4. -19 - (-81) = -19 + 81 = 62
5. -2,5 - 1,9 = -4,4
6. \frac{3}{16} + \frac{5}{12} = \frac{3 \cdot 3}{16 \cdot 3} + \frac{5 \cdot 4}{12 \cdot 4} = \frac{9}{48} + \frac{20}{48} = \frac{29}{48}
7. -\frac{10}{11} - (-\frac{10}{11}) = -\frac{10}{11} + \frac{10}{11} = 0
8. 1\frac{2}{9} + (-\frac{2}{27}) = \frac{11}{9} - \frac{2}{27} = \frac{11 \cdot 3}{9 \cdot 3} - \frac{2}{27} = \frac{33}{27} - \frac{2}{27} = \frac{31}{27}

Ответ: 1) -5; 2) 23; 3) -37; 4) 62; 5) -4,4; 6) \frac{29}{48}; 7) 0; 8) \frac{31}{27}