Answer: The required total cost of the meal is $73.525.
Step-by-step explanation: Given that Mario takes his best friend out for lunch, the total bill is $86.50 and he leaves a 15% tip.
We are to find the total cost of the meal.
The total cost of the bill is equal to the difference of the total bill and the amount that was left for tip.
The amount of the tip is given by
![15\%*86.50=(15)/(100)*86.50=12.975.](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mr9twfucqkosu90i19bcrrfsopumbx9s0y.png)
Therefore, the total cost of the meal is
![\$(86.50-12.975)=\$73.525.](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gp6ukzou3qjjl0646epe2pgq6ppfrutpi1.png)
Thus, the required total cost of the meal is $73.525.