Question

You have $100 saved and a plan to save $20 each month. Write a rule for the amount saved (in dollars) as a function of the number of months from now.

x | y
0 | 100
1 | 120
2 | 140
3 | 160
4 | 180
5 | 200
6 | 220
7 | 240
8 | 260
9 | 280
10| 300
11| 320
12| 340

Answer 1

y = 20x + 100

Answer 2

Because you already have 100 dollars that will be your starting point (or your y-intercept). Then you are saving 20 dollars every month. "x" stands for the number of months.
So for example:

Say you have saved up for 4 months so far. You would plug 4 into the x value:
y = 20x + 100
y = 20(4) + 100
y=80 +100
y= 80
(you can check your chart for confirmation.)