Question

Lia must work at least 5 hours per week in her family’s restaurant for $8 per hour. She also does yard work for $12 per hour. Lia’s parents allow her to work a maximum of 15 hours per week overall. Lia’s goal is to earn at least $120 per week.
Write a system of inequalities to represent this situation. Let r be the number of hours worked at the restaurant, and let y be the number of hours of yard work.
Graph the inequalities.
What is the maximum number of hours Lia can work at the restaurant and still meet her earnings goal? Explain.
What is the maximum amount of money Lia can earn in 1 week? Explain.

Answer 1

As the question states, let r be the number of hours worked at the restaurant, and y be the number of hours of yard work. 
We know that she can only work a maximum of 15 hours per work total, and that at she must work at least 5 hours in the restaurant. 
Therefore:
r + y ≤ 15
r ≥ 5
We also know that she wants to earn at least 120 dollars, earning $8/hr in the restaurant and $12/hr in the yard:
8r + 12y ≥ 120

What is the maximum of hours Lia can work in the restaurant and still make at leas 120 hours? 
Lia's parents won't let her work more than 15 hours, so we know that the answer won't be higher than 15.
If she worked all 15 hours in the restaurant, she would make 8*15 = 120.
The maximum number of hours she can work in the restaurant is therefore 15 hours

What is the maximum amount of money Lia can earn in a week? 
Lia has to work a minimum of 5 hours in the restaurant. She makes more money doing yard work, so she should devote the rest of her available work hours to yard work.
That means that, given her 15 hour work limit, she will maximize her income by working 5 hours in the restaurant and 10 hours in the yard. 
5*8 + 10*12 = 40 + 120 = 160
The most she can make is 160 dollars, working 5 hours in the restaurant and 10 hours in the yard