ANSWER
[tex]C=\frac{2}{15}x[/tex]EXPLANATION
The commission that Leah earns is proportional to the amount of shirts that she sells.
The general form of a proportional relationship is:
[tex]y=kx[/tex]where k = constant of proportioality
Let the amount of commission she earns be C.
Let the amount of shirt she sells be x.
She earns $16 for every $120 of shirts that she sells. This means that:
[tex]\begin{gathered} 16=k\cdot120 \\ \Rightarrow k=\frac{16}{120} \\ k=\frac{2}{15} \end{gathered}[/tex]Therefore, we have that the equation that gives the total commission C is:
[tex]C=\frac{2}{15}x[/tex]