Question 423760
Solutions:

16 + 8r - 4r + 4 = 24
16 + 4r + 4 = 24
20 + 4r = 24
20 - 20 + 4r = 24 - 20
4r = 4
Dividing both sides by 4, we get
4r/4 = 4/4
r = 1