The New York State Fair charges $15 for admission plus $0.40 per ride ticket. Let t represent the number of tickets bought. Write and expression to determine how much you will spend at the carnival.

15 is your constant, because you have to pay $15 regardless. The 40 cents is not constant— because we don’t know how many tickets we bought! therefore:

15 + 0.40t = how much you’d spend at the carnival!