Which expression is equivalent to x2-16 ?

Abiologist 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. which equation represents this situation? a. f – 52 = 63 b. f – 63 = 52 c. 63 – f = 52 d. f – 63 = –52

If x + 10 = 70, what is x? a. 40 b. 50 c. 60 d. 70 e. 80

Can someone me with this problem i don't understand i need