A ride costs $3, then [tex]r[/tex] number of rides costs [tex]3 \times r = 3r[/tex]. As she takes more rides, her initial value of $35 will decrease by [tex]3r[/tex]. Re-writing this expression gives [tex]m = 35 - 3r[/tex], where [tex]m[/tex] is the amount of money she has.
[tex]m = 35 - 3r[/tex] can also be re-written as [tex]m = -3r + 35[/tex]
