If she gets 12 out of 15 right, then you will get the fraction 12/15 showing the amount of times she has gotten it right. Divide both 12 and 15 by 3 because that is the least common multiple. That gives you the fraction 4/5 which means that 4/5 times she answers, she will get the answers right. So, since the denominator, 5, goes into 25, 5 times, you will also multiply 4 by 5 giving you 20. So Matilda will get 20/25 problems correct
Answer: 20