x+=91
x-=8.9
x=5.1
÷x=63
5y-y=4.8
x+3.67=8 2.4x=122.5x÷4=62.5 0.6x-0.4x=1
解:12-x+□=2.8◯□
2.8+x=12
2.8+x-2.8=12◯□
x=□
解:6.3÷x◯x=0.7◯□
0.7×x=6.3
0.7x◯□=6.3◯□