Isolate the q. Note the equal sign. What you do to one side, you do to the other.
Subtract 4 from both sides
8q + 4 (-4) = 20 (-4)
8q = 20 - 4
8q = 16
Next, divide 8 from both sides to isolate the q
8q/8 = 16/8
q = 16/8
q = 2
q = 2 is your answer
hope this helps