Answer:
r = 2x + 7
Step-by-step explanation:
get r on one side
8x + 12 + 16 = 4r
divide both sides by 4 to get r by itself
8x/4 + 12/4 + 16/4 = 4r/4
2x + 3 + 4 = r
2x + 7 = r
or
