1)
1/8 * 56 = 56/8 = 7
7/9 * 810 = (7*810)/ (9*1) = (7*90)/(1*1) = 630
2)
12 : 1/6 = 12 * (6/1) = 12 * 6 = 72
28 : 4/7 = (28/1) * (7/4) = (7*7)/(1*1) = 49
3)
1)2/3 * 60 = (2*60)/3 = 120/3 = 40 (км/ч) скорость слона
4)
1) 30 : 2/5 = 30/1 * (5/2) = 150/2 = 75 (открыток) у Оли