-39 + 42 = 3
-17 + (-20) = -17 - 20 = -37
28 + (-35) = 28 - 35 = -7
-16 - (-10) = -16 + 10 = -6
-4,3 - 6,2 = -10,5
Приведем дроби к общему знаменателю 18:
-\(\frac{7}{9}\) - \(\frac{1}{6}\) = -\(\frac{7\cdot2}{9\cdot2}\) - \(\frac{1\cdot3}{6\cdot3}\) = -\(\frac{14}{18}\) - \(\frac{3}{18}\) = -\(\frac{14+3}{18}\) = -\(\frac{17}{18}\)
Ответ: a) 3; б) -37; в) -7; г) -6; д) -10,5; е) -\(\frac{17}{18}\)