A biologist is recording the loss of fish in a pond. He notes the number of fish, f, in the pond on June 1. On July 1 there were 63 fish in the pond, which is 52 fewer fish than were in the pond on June 1. What is the number of fish in the pond on June 1?

63−f=52

f−52=−63

f−52=63

f−63=−52