To find the rate of change, you look at how much the y value increases with a change of 1 x. We see that as x increases from 1 to 2, y increases from 120 to 144. Then we subtract 144-120 to find the rate of change, which is just 24 (also note that x changes by 1 here).
Then for the initial value:
We see that y increases by 24 for 1 x, so subtracting the value at x=1 by 24 we get 120-24 = 96, which is the initial value.
Hope this helps
