how do you solve 9x - 7 = -7 and the question on the picture

Answer:
x = 0
r = 20
Step-by-step explanation:
9x - 7 = -7
add 7 to each side of the equation:
9x = 0
x = 0
-4 = (r/20) - 5
add 5 to each side of the equation:
1 = r/20
multiply both sides by 20:
r = 20