1)
213(x-89)=9585
x-89=45
x=45+89
x=134
2.
4848:(60-x)=101
4848/60-x=101
4848=101(60-x)
48=60-x
x=60-48
x=12
3.
(x+51)*309=16686
309x+15759=16686
309x=16686-15759
309x=927
x=3
4.
9435:(77-x)=555
9435:(77-x)=555
9435/77-x=555
9435=555(77-x)
17=77-x
x=77-17
x=60