We first determine the cost of one pair, that is:
[tex]c=\frac{189}{3}\Rightarrow c=63[/tex]So, each pair of shoes cost $63.Now, we determine the value of the commission:
[tex]v=\frac{63\cdot17}{100}\Rightarrow v=10.71[/tex]So, the commission for each pair of shoes is $10.71, now we multiply this by 3 times. That is:
[tex]10.71\cdot3=32.13[/tex]So, the commission for the three pairs of shoes will give him $32.13.