Выполните действие (3-4) а) 1/9+2/3 б)2 3/4+1/5 --------------------- а)7/8-1/3 б)1 5/7-4/5

Приведем дроби к общему знаменателю и выполним действия:

1) 1/9 + 2/3 = 1/9 + (2 * 3)/(3 * 3) = 1/9 + 6/9 = (1 + 6)/9 = 7/9;

2) 2 3/4 + 1/5 = 2 + 3/4 + 1/5 = 2 + (3 * 5)/(4 * 5) + (1 * 4)/(5 * 4) = 2 + 15/20 + 4/20 = 2 + (15 + 4)/20 = 2 + 19/20 = 2 19/20;

3) 7/8 - 1/3 = (7 * 3)/(8 * 3) - (1 * 8)/(8 * 3) = 21/24 - 8/24 = (21 - 8)/24 = 13/24;

4) 1 5/7 - 4/5 = 1 + 5/7 - 4/5 = 1 + (5 * 5)/(7 * 5) - (4 * 7)/(5 * 7) = 1 + 25/35 - 28/35 = 1 + (25 - 28)/35 = 1 - 3/35 = 35/35 - 3/35 = (35 - 3)/35 = 32/35.