Given data:
$39 for unlimited rides
$12 for admission plus $1 per ride
Let x be the number of rides
Let y be the cost in terms of the number of rides
First option is always $39 (it doesn't depend of the number of rides)
[tex]y=39[/tex]Second option is $12 plus $1 multiplied by the number of rides:
[tex]y=12+1x[/tex]System of equations:
[tex]\begin{gathered} y=39 \\ y=12+x \end{gathered}[/tex]The two options wind up costing the same amount when the equations are equal:
y=y
Subtitute the value of y corresponding in each equation:
[tex]39=12+x[/tex]Solve x:
[tex]\begin{gathered} 39-12=12-12+x \\ 27=x \\ \\ x=27 \end{gathered}[/tex]