1.X-4×2/3=2/3X
X-8/3=2/3X
X-2/3X=8/3
1/3X=8/3
X=8/3除1/3
X=8
2.1/8(X+0.5)=75%
X+0.5=75%除1/8
X+0.5=6
X=6-0.5
X=5.5
3.3又5/4X+1.2X=25
17/4X+1.2X=25
4.25X+1.2X=25
5.45X=25
X=25除5.45
X=
4.2×(×-0.7)=4.8
X(X-0.7)=4.8除2
X(X-0.7)=2.4
2X-0.7=2.4
2X=2.4+0.7
2X=3.1
X=3.1除2
X=1.55
5.3乘还是除啊?