The number of hours that we ski is a variable cost where each hour costs $60. On top of that, we have a fixed cost of $20 which stays the same no matter how long we ski.
So we can use an equation to find the totla cost C given the number of hours t as follows:
C(t) = 60t + 20
We can use this equation to find the cost of a skiing session by plugging in some value for t. For example, if we ski for 3 hours:
C(3) = 60(3) + 20 = $200
The equation can also be written using x and y and mean the same thing.
