Given:
Amount he earns lifeguarding = $19 per hour
Amount he earns clearing table = $9 per hour
Maximum amount of hours he can work in a week = 14 hours.
This is expressed as: e + y ≤ 14
Minimum amount he must earn = $180.
This is expressed as: 19e + 9y ≥ 180
Let e represent the number of hours lifeguarding
Let y represent the number hours clearing tables.
We have the system of inequaties:
19e + 9y ≥ 180......................inequality 1
e + y ≤ 14................................inequality 2
Let's solve for y using substitution method.
Subtract y from both sides in inequality 1:
e + y - y ≤ 14 - y
e ≤ 14 - y
Substitute (14 - y) for e in inequality 1:
19(14 - y) + 9y ≥ 180
266 - 19y + 9y ≥ 180
266 - 10y ≥ 180
Subtract 266 from both sides:
266 - 266 - 10y ≥ 180 - 266
-10y ≥ -86
Divide both sides by -10:
Solving further:
Therefore, the number of hours Ian must use in clearing the tables should be no more than 8.6 hours
To solve for e, substitute 8.6 for y in either of the inequalities.
Substitute 8.6 for y in inequality 2:
The graph of the inequalities is below:
e + y ≤ 14
e + 8.6