Explanation

If the amount in May is M and the amount in April is A, then the question tells us



Then it tells us that , so we have





I'm prepared to do long division if necessary, but since and , . Then all we have to do is take the decimal point into consideration - although we can see the answer will be (B). 115 goes into 345 three times, so something a hundred times smaller goes in a hundred more times. Lastly, we can do a sanity check. This is April's number, and it should be smaller than May's. It is. Indeed, 15% of 300 is 10% plus half of 10%, so it's .

The correct answer is (B).