6(x+16)=150 56: x+12=19 76-(15-a)=69 144: (x-3)=36

1.
6х+96=150
6х=150-96
6х=54
х=9

2.
56/х+12=19
56/х=19-12
56/х=7
х=56/7
х=8

3.
76-(15-а)=69
76-15+а=69
а=69-76+15
а=5

4.
144/(х-3)=36| ×(х-3)
144=36(х-3)
144=36х-108
36х=144+108
36х=252
х=252/36
х=7