Answer:
28 weeks
Step-by-step explanation:
She starts with $500.
She adds $40 per week. In w weeks, she adds 40w.
After w weeks, she has 500 + 40w.
The total must equal $1620.
500 + 4w = 1620
Subtract 500 from both sides.
4w = 1120
Divide both sides by 40.
w = 1120/40 = 28
Answer: 28 weeks
