1) 84а+25а+7=443
84а+25а=443-7
109а=436
а=436:109
а=4
2) 4(9+7х)+21=393
36+28х+21=393
28х=393-36-21
28х=336
х=336:28
х=12
3) 486:(5х+2)=18
97.2х+243=18
97.2х=18-243
97.2х=-225
х=-225:97.2
х=-2.31
4) 5(14+b+6b)=158
70+5b+30b=158
5b+30b=158-70
35b=88
b=88:35
b=2.51