Answer:
She paid back $192 in interest
Step-by-step explanation:
A = P(1+r)^n
P = $1,200
r = 10.5% = 0.105
n = 18 months = 18/12 = 1.5 years
A = 1,200(1+0.105)^1.5 = 1,200(1.105)^1.5 = 1,200×1.16 = 1,392
Amount = $1,392
Principal = $1,200
Interest = amount - principal = $1,392 - $1,200 = $192