Math Question please help

Let c = weight of cat.

Let d = weight of dog.

      d = 8c                  (the dog weights 8 times as much as the cat)

d + c = 54                  (together, they weigh 54 pounds)

Substitute  8c  for  d  from the first equation into the second equation:

8c + c = 54

      9c = 54

        c = 6

if c = 6, the d= 8c = 8(6) = 48.

her cat weighs 6 pounds and her dog weighs 48 pounds. i hope this helps :)