The formula for simple interest is:
A = P(1+rt)
Where P = amount borrowed
r = interest rate
t = time of loan
A = 5000(1 + 0.125*2)
A =6,250
The total amount she paid back was $6,250
For her monthly payment divide total paid back by 24 months ( 2 years = 24 months)
6250 / 24 = 260.42
Her monthly payment was $260.42