Question 853440
You're trying to find the equality, so set the values against each other.
Let X be the number of weeks until equality.
160 + 7x = 210 + 5x (what you receive set against what he receives)
Subtract 160 from each side
7x = 50 + 5x
Subtract 5x from each side
2x = 50
Divide each side by 2
x = 25
It will take 25 weeks.
.
let's prove this.
In 25 weeks, you will have $7 * 25 = $175 + the 160 you started with = $335
In 25 weeks, your friend will have $5 * 25 = 125 + the 210 he started with = $335
Success!