for number 3.
You add 8 to both sides as you need to separate the variable
4x-8=32
+8 +8
4x=32
now divide 32 by 4
x=8
for number 4
you use pemdas to multiply the parenthisis
2(x-5)=-20
(2•x)-(2•5)
2x-10=-20
then add 10 to both sides
2x-10=-20
+10 +10
2x=10
divide 10 by two
x=5