Standard form: Ax + By = C
Equation: 12x + 15y = 120
In order to determine the balance of the account, use the following formula for the amount of money obtained after t years, basen on a compound interest:

where,
P: principal = $12,500
A: amount earnt after t years = ?
r: interest rate in decimal form = 0.045 (4.5%)
n: times at year for the compund interes = 4 (quaterly)
Replace the previous values of the parameters into the formula for A and simplify:

Hence, the balance after 8 years is approximately $17,880.64 in the account.
The interest earnt by the account is given by the difference between the previous result and the principal invesment:
I = $17,880.64 - $12,500 = $5,380.64
Hence, the interest earnt is $5,380.64
By graphing the polynomial, we conclude that there is only one real root, so the correct option is A.
<h3>
How many roots has the given polynomial?</h3>
We have the polynomial:

To see how many real roots this polynomial has, we can graph it and see how many times the graph intercepts the x-axis.
The graph can be seen below:
There we can see that there is only one intercept, so there is only one real root.
So the correct option is A.
If you want to learn more about polynomials:
brainly.com/question/4142886
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No, the slope is just one so you would rise one and go over one. The 4 represents the y-intercept so you would start at the point (0,4) then go from there.