I think the problem is simple interest the principal is separated from the interest.
first, P 25 000 is subtracted to P 10 000 and you'll get P 15 000
then your final principal is P 15 000
then get the simple interest:
P = P 15 000
R = 14 %
T = 4 months
then use the formula for finding the simple interest:
Simple interest = principal x rate x time or S = p x r x t
Simple interest = P 15 000 x 0.14 x 4 =
simple interest = P 8 400
so, Mrs. Gillera pay P8 400 in the last payment.
how many times she pay ?
so divide P 25 000 to the simple interest and you'll get 3.
therefore, Mrs. Gillera pay 3 times.