Найдите сумму дробей: 1)3/8+1/3; 2)2/5+7/10; 3)1/7+1/14+1/21.
3/8+1/3=9/24+8/24=17/24 2/5+7/10=4/10+7/10=11/10 = 1 1/10 1/7+1/14+1/21=6/42+3/42+2/42=11/42