You are solving for the variable (c).
Note the equal sign, what you do to one side, you do to the other. Do the opposite of PEMDAS (Parenthesis, Exponents (& roots), Multiplication, Division, Addition, Subtraction)
First, subtract 8 from both sides
4c + 8 (-8) = 20 (-8)
4c = 20 - 8
4c = 12
Next, to fully isolate the variable (c), divide 4 from both sides
(4c)/4 = (12)/4
c = 12/4
c = 3
3 is your answer for c.
~
