To find the total dollar amount Groan earned this month from both jobs, we can set up an expression based on the number of hours he worked as a tutor and a waiter.
Let:
- \( t \) = number of hours Groan worked as a tutor
- \( w \) = number of hours Groan worked as a waiter
From the problem statement, we know that:
- The hourly pay for tutoring is $13,
- The hourly pay for waiting is $12,
- The total number of hours worked at both jobs is 109 hours.
We can express the number of hours worked as a waiter in terms of \( t \): \[ w = 109 - t \]
Now, we can express the total earnings from both jobs:
- Earnings from tutoring: \( 13t \)
- Earnings from waiting: \( 12w = 12(109 - t) \)
Now, putting it all together, the total earnings \( E \) can be expressed as: \[ E = 13t + 12(109 - t) \]
Now, let's simplify this expression: \[ E = 13t + 12 \times 109 - 12t \] \[ E = (13t - 12t) + 1308 \] \[ E = t + 1308 \]
Therefore, the expression for the combined total dollar amount Groan earned this month is: \[ E = t + 1308 \]