Giúp mình bài này với

Giải thích các bước giải:

`(x-12).13=0`
`x-12=0`
`x=12`
Vậy `x=12`
`12.(45-x)=12`
`45-x=1`
`-x=-45+1`
`-x=-44`
`x=44`

Vậy `x=44`
`21(34-x)=42`
`34-x=2`
`x=32`
`(3-x).57=57`
`3-x=1`
`-x=-3+1`
`-x=-2`
`x=2`
`(x-2)+150=240`
`x-2=240-150`
`x-2=90`
`x=90+2`
`x=92`
`(x+72)-180=75`
`x+72=75+180`
`x+72=255`
`x=183`
`300-(x+163)=65`
`300-x-163=65`
`-x+137=65`
`-x=-72`
`x=72`
`2x+7x=918`
`9x=918`
`x={918}/9`
`x=102`
`(x-16)-135=10`
`x-16=10+135`
`x-16=145`
`x=145+16`
`x=161`
`473-x-68=363`
`-x+405=363`
`-x=-42`
`x=42`
Vậy `x=42`