To solve this problem we are going to use the simple interest formula:

where

is the sum of the <span>interest and the principal
</span>

is the principal

is the interest rate in decimal form

is the time in years
<span>
We know for our problem that </span>

,

, and

. Now, let

represents our interest rate. To express the interest rate in decimal form, we are going to divide the rate by 100%:


.
Now that we have all the values we need, lets replace them in our simple interest formula to find the interest rate:

![21000=15000[1+(0.01x)(5)]](https://tex.z-dn.net/?f=21000%3D15000%5B1%2B%280.01x%29%285%29%5D)




We can conclude that the interest rate of your cousin's loan was 8%.
64/81 is the answer.
8 x 8 64
——— = —
9 x 9 81
(5,0) is the x-intercept because when you plug 0 in for y, x=5.
(0,4) is the y-intercept because when you plug in 0 for x, y=4.