Marlon goes fishing for 5 days. He catches 7 fish and releases 3 fish each of the 5 days.

He catches 7 and releases three, this means he subtracts 3 so you woyld have 7-3

He does this for 5 days, so you would multiply it by the number of days.

The correct equation would be 5 x (7-3)

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value