At the veterinarian’s office, terri learned that her dog weighed 4 times as much as her cat. together the pets weighed 40lbs. how much did the dog weigh

32lbs. You take 4 and multiply it by 8 which gives you 32, the dog weighs 32lbs, then you have 8 left over, the cat weighs 8lbs.

5x = 40 (if x represents the cat's weight, and 4x represents the dog's)
40/5= 8
so the cat weighs eight pounds. 
8 x 4 = 32
the dog weights thirty two pounds. 
since 32 + 8 = 40, it's correct!