1)
84а+25а+7=443
109a=443-7
109a=436
a=436:109
a=4
-----------.
2)
4(9+7х)+28=400
36+28x+28=400
28x+64=400
28x=400-64
28x=336
x=336:28
x=12
--------------
3)
486÷(5х+2)=18.
5x+2=486:18
5x+2=27
5x=27-2
5x=25
x=25:5
x=5
-----------
4)
35(14+b)-476+6b=383
490+35b-476+6b=383
41b+14=383
41b=383-14
41b=369
b=369:41
b=9