Answer:
$80
Explanation:
We know the following information:
- there are 5 school days in 1 week
- Chris makes $4 each school day
We are solving for how much money Chris will make in a month.
First, we can solve for how much money Chris makes in 1 week:

So, Chris makes $20 in 1 week.
Next, we can solve for how much money Chris will make in a month using our knowledge of how long a month is. Over the course of 1 month on the Gregorian Calendar (excluding the month of February), there are 4 weeks. Therefore, we can compute how much money he makes in a month with the following equation:

So, Chris will make $80 in a month.