Stray cats loved eating goldfish in the pond leaving w goldfish. Paige had raised x goldfish in the pond initially. How many goldfish disappeared?
We are given that Paige had raised x goldfish in the pond initially. We are also given that the stray cats loved eating goldfish in the pond, leaving w goldfish. 

From this, we can infer that the number of goldfish that disappeared is equal to x - w.