Вычислите: а)-2/3+3/4 б)-1¾+1¹/6 в)7/9-5/6 г)-7/12+3/4

Вычислим значения выражений: 

а) -2/3 + 3/4 = (-2 * 4 + 3 * 3)/12 = (-8 + 9)/12 = (9 - 8)/12  = 1/12; 

б) -1 ¾ + 1 ¹/6 = -1 - 3/4 + 1 + 1/6 = -3/4 + 1/6 = 1/6 - 3/4 = (1 * 2 - 3 * 3)/12 = (2 - 9)/12 = -7/12; 

в) 7/9 - 5/6 = (7 * 2 - 5 * 3)/18 = (14 - 15)/18 = -1/18; 

г) -7/12 + 3/4 = 3/4 - 7/12 = (3 * 3 - 7 * 1)/12 = (9 - 7)/12 = 2/12 = 2/(2 * 6) = 1/(1 * 6) = 1/6.