Question

Which is the function that gives the amount of money m that Margaret has as a function of the number of rides r that she takes ?

Answer 1

A ride costs $3, then $r$ number of rides costs $3 \times r = 3r$. As she takes more rides, her initial value of $35 will decrease by $3r$. Re-writing this expression gives $m = 35 - 3r$, where $m$ is the amount of money she has.

$m = 35 - 3r$ can also be re-written as $m = -3r + 35$