If Ed has 2 dogs and 3 cats he has in total 2 + 3 = 5 pets that are not fish. If Ed has twice as many cats and dogs combined he has 2 * 5 = 10 fish. Therefore, in total Ed has 5 + 10 = 15 pets.
This justifies what answer for what question? Q & A:
Ed has 2 dogs, 3 cats and twice as many fish as cats and dogs combined. How many pets does Ed have in total?
15