7/12-8/15=?
[8\15-(7\12-2\5)]*15\14=?
7/15+7/12+8/15-7/12 简算
(7/12-8/15)*36
1/15+7/12+8/15-7/12
用简便方法计算.5/12+7/15+8/15+7/12=、1--3/7--2/7=、3/4+8/14--1/4--1/1
15/16+7/12=
7/12+8/15+5/12-8/15 = (能用简便方法计算就用简便方法计算.)
(12x-10)/21+(7x-9)/20=(2-x)/15+(8x-9)/12
7+8=15,15-7=8,15-8=7;
8/9-5/12= 7/15-3/20-1/20+3/15 =(7/15+3/15)-(3/20+1/20) =10/1
(8/10)+(x/15)=(8/12)+[(8-x)/15]