Let the number of extra hours she baby sits every day is x.
For x hours she will make: 4x = 4x
For three days a week = 34x = 12x.
The base of $5 for showing up.
For 3 days a week of showing up = 3* $5 = $15
Total = 12x + 15
Therefore total amount for 3 days a week = $(12x + 15), where x is the number of hours spent every day.