[tex]\begin{gathered} \text{let} \\ y=\text{proceed from a car wash} \\ x=\text{ numbers of car washed} \\ y=kx \\ \text{where} \\ k=\text{constant of proportionality} \\ y=kx \\ 180=9k \\ k=\frac{180}{9} \\ k=20 \\ \text{amount raise when 60 cars is washed can be solved as follows} \\ y=kx \\ x=60 \\ y=20\times60 \\ y=1200 \end{gathered}[/tex]
amount raised = $ 1200
