You and your friends are at an amusement park. Some of you have not yet decided whether or not you want to go. If tickets cost $20 each, write the amount (in dollars) that you will spend as a function of the number of tickets you buy. Let t represent one ticket, and c represent the total cost in dollars.
Each ticket costs $20. This means that for every one of you who goes in, the total cost increases by $20. This is represented by the equation c = 20t.