y and x are not constants, so you don’t have to find the value of them.
On the other hand, you do have to find m and b. M is the slope and B is where the y-axis is crossed, or what her balance was at week 0.
To find slope: (y1-y2)/(x1-x2) or the rise over run.
130-280= -150
2-8= -6
-150/-6= 25= m
This means she adds $25 each week.
To find the y-intercept: this is where x=0 and y is some unknown value. We are given the amount at the end of 2 weeks, so we just need to go back 2 weeks. She adds $25 each week. -2 weeks • 25 = -$50
130-50= 80 = b, or the initial amount in the account.
We need to plug b and m into the equation.
y=25x+80
