In order to get the average hourly wage we have to compute the total earnings and then divide it by the total hours:
[tex]\begin{gathered} E=(28\cdot3.15)+18+16+20+30+18=190.2 \\ Av=\frac{E}{t}=\frac{190.2}{28h}=6.79 \end{gathered}[/tex]Therefore, the average hourly wage is 6.79 dollars per hour. Answer d.