5/8乘X+(84-X)乘3/4等于57 等于5/8X+63-3/4X等于57 等于-1/8等于-6 X等于48
5/8乘x+(84-x)乘3/4=57
5/8乘x+84乘3/4-x乘3/4=57
(3/4-5/8)乘x=63-57
1/8乘x=6
x=6÷1/8
x=48
8/5X+63-4/3X=57
8/5X-4/3X=57-63
8/5X-8/6X=-6
-8/1X=-6
两边同乘-8
X=48
5x/8+3/4[84-x]=57
5x/8+63-3x/4=57
-1x/8=-6
x=3/4