The applicable formula is
I = Prt
where P = the principal value (12109), r is the interest rate (0.045), and t is the time period in years (1/2)
a) Substituting the given values, the interest amount is computed as
I = ($12,109)(.0.45)(1/2)
I = $272.45
b) The amount Sophia will have to pay back is the sum of the principal amount and the interest owed.
$12,109 + 272.45 = $12,381.45
Draw the graph for each side, member, of the equation and see where the curves cross, are equal. The x values of these points, are the solutions to the equation.
Greetings, the answer is 11.