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
        
             
        
        
        
Answer:13xy+5y
Step-by-step explanation:
 
        
             
        
        
        
3 16 
Explanation
 Factor the numerator and denominator and cancel the common factors.
        
             
        
        
        
Answer:
18
Step-by-step explanation:
2x9=18
 
        
             
        
        
        
Answer:
6√3
Step-by-step explanation:
6^2+x^2=12^2
36+x^2=144
-36          -36
x^2=108
x=6√3