[tex]\begin{gathered} \text{ \$56 for 7 hours} \\ So,\text{ for 1 hours }\Rightarrow\frac{\text{ \$56}}{7}=\text{ \$8} \\ So,\text{ for making \$72 , he needs to babysit of} \\ \Rightarrow\frac{\text{ \$72}}{\text{ \$8}}=9\text{ hours} \end{gathered}[/tex]