I = 42t
When t = 5, I = 42*5 = 210
When t = 6, I = 42*6 = 252
When t = 7, I = 42*7 = 294
When t = 8, I = 42*8 = 336
When t = 9, I = 42*9 = 378
When t = 10, I = 42*10 = 420
The initial expression is:

So we can solve for r so:
Answer:
8x^2 + 15x -9
Explanation:
Distribute and combine
Answer:
15 years and 8 months
Step-by-step explanation:
I used the formula for compound interest as shown below and solved for the unknown, time.
Since our interest is compounded annually (So once a year) our m value is 1.