Remember to follow PEMDAS. Remember that the goal is to isolate the x.
First, distribute 4 to all terms within the parenthesis. Remember the signs.
4(-x + 4) = -4x + 16
-4x + 16 = 12
Next, isolate the x. Note the equal sign. What you do to one side, you do to the other. Do the opposite of PEMDAS. First, subtract 16 from both sides.
-4x + 16 (-16) = 12 (-16)
-4x = 12 - 16
-4x = -4
Next, isolate the x. Divide -4 from both sides
(-4x)/-4 = (-4)/-4
x = -4/-4
x = 1
1 is your answer for x.
hope this helps