Question

John starts a saving account with $100. Every week he adds $6 to his account. Which equation can be used to determine the number of weeks w, after which John's accounts reaches $220?

Answer 1

Starts at 100, so 100 is b in the equation y = mx + b

Since 6 is a constant addition addition through a period of time, it is the slope, or m, so we have y = 6x + 100, where y equals the money in john's account

We are given that it's 220, so y = 220.

220 = 6x + 100

220 - 100 = 6x + 100 - 100

120 = 6x

120/6 = 6x/6

20 = x

x = 20, so after 20 weeks John has 220 dollars.