Answer: $79.12
Step-by-step explanation:
[tex]$5 peopleeach order is worth \$12.80$\begin{aligned}\therefore \text { Total bill } &=12.80 \times 5 \\&=64 \$\end{aligned}$[/tex]
[tex]${Tax}: 7.5 \%$\therefore$ Bill after tax$\begin{aligned}&=64\left(\frac{100+7.5}{100}\right) \\&=64(1.075) \\&\text{Bill \ with \ tax}=68.8 \$\end{aligned}$[/tex]
[tex]$Gratuity$=15 \%$ of bill with tax$\begin{aligned}\therefore \text { Gratuity} &=0.15 \times 68.8 \\&=10.32 \$\end{aligned}$$\therefore$ Ended up paying a total of $=68.8+10.32$$\ \ \ \ \ \ \ \ \ \ =\$79.12 $[/tex]