解:x-42=36
x=
解:x÷5.7=85.7
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◯□