1) Вычислите: 12/35 : 6/7 + 3/10

12/35 : 6/7 + 3/10 = (12/35 * 7/6) + 3/10 = (12*7)/(35*6) + 3/10 = 84/210 + 3/10 = 2/5 + 3/10 = 4/10 + 3/10 = 7/10.