1) 4(9+7х)+21=393 2) 486: (5х+2)=18 3) 5(14+b)+6b=158

1)    4(9+7х)+21=393
36+28х+21=393
28х=393-36-21
28х=336
х=336:28
х=12
2)   486:(5х+2)=18
97.5х+243=18
97.5х=18-243
97.5х=-225
х=-2.3
3)   5(14+b)+6b=158
70+5b+6b=158
5b+6b=158-70
11b=88
b=8