What is the price after tax for a $940 iPhone with a NJ sales tax of 6.625%?

Find how long it take to have the same balance
Write the expressions represent the savings of Jen and the savings of Jason
For an instance, w stands for the number of weeks they take to have the same balance.

Jen ⇒ initial $350, additional $25/week, the expression will be
350 + 25w
Jason ⇒ initial $470, additional $15/week, the expression will be
470 + 15w

Then find the value of w using equation Jen's expression and Jason's expression
350 + 25w = 470 + 15w
25w - 15w = 470 - 350
10w = 120
    w = 120/10
    w = 12

They have the same balance in 12 weeks

Find how much each of them has in 12 weeks
350 + 25w
= 350 + 25(12)
= 350 + 300
= 650

They have each $650 in 12 weeks