All you do is plug in the numbers 4, 10 & 20 for w to get that amount of money earned after that meant weeks.
Part A
After 4 weeks- $57
After 10 weeks- $75
After 20 weeks- $105
Part B
You wouldn’t have enough money because if you plug in 20 for w it only equals 105$.
45+3(20)
45+60=105