Let the weight of Paula's dog be x
Let the weight of Carla's dog be y
We know that the weight of Paula's dog is 3 times that of Carla's dog, therefore:
x = 3y ...........> equation I
We also know that the sum of the weights is 48 pounds, therefore:
x + y = 48 ............> equation II
Substitute with equation I in equation II:
3y + y = 48
4y = 48
y = 12 pouds
Substitute with the value of y in equation I:
x = 3(12) = 36 pounds
Based on the above calculations:
Paula's dog weighs 36 pounds
Carla's dog weighs 12 pounds