Выполните умножение: 1) 2/3 * 9/10; 2) 2целых 3/5 * 1целая 9/26; 3) 7/19 * 57целых заранее )

2/3 * 9/10 = (2 * 9) / (3 * 10) = (2 * 3 * 3) / (3 * 5 * 2) = 3/5 = 0,6

2 3/5 * 1 9/26 = (2 * 5 + 3)/5 * (1 * 26 + 9)/26 = 13/5 * 35/26 =

= (13 * 35) / (5 * 26) = (13 * 5 * 7) / (5 * 2 * 13) = 7/2 = 3,5

7/19 * 57 = (7 * 57)/19 = (7 * 3 * 19)/19 = 7 * 3 = 21