Answer:
60 lb
Explanation:
Represent the weights of the dogs by P and C. Then P = 3C.
Then P + C = 80, or, after substitution of 3C for P,
3C + C = 80, or
4C = 20, so that C = (20 pounds)
Paula's dog weighs 3 times as much as Carla's: P = 3(20 lb) = 60 lb