Lia must work at least 5 hours per week in her family's restaurant for [tex]\$8[/tex] per hour. She also does yard work for [tex]\$12[/tex] 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 [tex]\$120[/tex] per week. Let [tex]r[/tex] be the number of hours worked at the restaurant, and let [tex]y[/tex] be the number of hours of yard work:

[tex]\[
\begin{array}{l}
r \geq 5 \\
r + y \leq 15 \\
8r + 12y \geq 120
\end{array}
\][/tex]

1. Graph the inequalities.

2. What is the maximum number of hours Lia can work at the restaurant and still meet her earnings goal? Explain.

3. What is the maximum amount of money Lia can earn in 1 week? Explain.



Answer :

Certainly! Let's break down the steps to solve the problem step-by-step:

### Given Information:
- Lia must work at least 5 hours per week in the restaurant ([tex]$r \geq 5$[/tex]).
- She can work a maximum of 15 hours per week overall ([tex]$r + y \leq 15$[/tex]).
- She wants to earn at least [tex]$120 per week ($[/tex]8r + [tex]$12y \geq 120$[/tex]).
- Hourly wage at the restaurant is [tex]$8 per hour. - Hourly wage for yard work is $[/tex]12 per hour.

We'll answer each part of the question:

### 1. Graph the Inequalities:

To graph the inequalities:
- [tex]$r \geq 5$[/tex]:
Draw a vertical line at [tex]$r = 5$[/tex] and shade to the right (including the line).
- [tex]$r + y \leq 15$[/tex]:
Draw a line passing through points [tex]$(15, 0)$[/tex] and [tex]$(0, 15)$[/tex]. Shade below this line (including the line).
- [tex]$8r + 12y \geq 120$[/tex]:
Rearrange to [tex]$y \geq \frac{120 - 8r}{12} \Rightarrow y \geq 10 - \frac{2r}{3}$[/tex].
Draw this line by finding intercept points, let’s find the intercepts:
- Set [tex]$r = 0 \Rightarrow y = 10$[/tex]
- Set [tex]$y = 0 \Rightarrow $[/tex] [tex]$r = 15$[/tex]

Plot these points [tex]$(0, 10)$[/tex] and [tex]$(15, 0)$[/tex], and shade above this line (including the line).

### 2. The Maximum Number of Hours Lia Can Work at the Restaurant:

To find the maximum number of hours Lia can work at the restaurant ([tex]$r$[/tex]) while still meeting her earnings goal of at least [tex]$120$[/tex], we need to analyze the constraints:
- [tex]$r \geq 5$[/tex] means she must work at least 5 hours at the restaurant.
- [tex]$r + y \leq 15$[/tex] means she wants to work no more than 15 hours in total.
- [tex]$8r + 12y \geq 120$[/tex] represents her earnings goal constraint.

We need to find the feasible values of [tex]$r$[/tex] and [tex]$y$[/tex] that satisfy all three conditions.

Evaluating these constraints, we can isolate the condition involving earnings:
[tex]\[ 8r + 12y \geq 120 \][/tex]

First, express [tex]$y$[/tex] in terms of [tex]$r$[/tex] from [tex]$r + y \leq 15$[/tex]:
[tex]\[ y \leq 15 - r \][/tex]

Substituting [tex]$y = 15 - r$[/tex] into the earnings constraint:
[tex]\[ 8r + 12(15 - r) \geq 120 \][/tex]
[tex]\[ 8r + 180 - 12r \geq 120 \][/tex]
[tex]\[ -4r + 180 \geq 120 \][/tex]
[tex]\[ -4r \geq -60 \][/tex]
[tex]\[ r \leq 15 \][/tex]

Since [tex]$r$[/tex] must also be at least 5:
[tex]\[ 5 \leq r \leq 15 \][/tex]

Thus, the maximum number of hours Lia can work at the restaurant while still achieving her earnings goal is 15 hours.

### 3. The Maximum Amount of Money Lia Can Earn in 1 Week:

Given that Lia can work a maximum of 15 hours at the restaurant (from part 2), we will find her total earnings:
[tex]\[ y = 15 - 15 = 0 \][/tex]

Lia would work all 15 hours at the restaurant and none doing yard work:

Total earnings:
[tex]\[ 8r + 12y = 8(15) + 12(0) = 120 \][/tex]

Thus, the maximum amount of money Lia can earn in one week is [tex]$120. This aligns well with the constraints and ensures that she meets her earnings goal of at least $[/tex]120.