If Marisa is going to estimate, then she needs to round each number. If she rounds to the nearest ones place, then she should have rounded 3.48 to 3 and rounded 7.33 to 7.
Marisa had rounded 3.48 to 4 and times it to 7.33 which she rounded to 8
In fact 3.48 is closer to 3 we know this since the .48 of 3.48 s below .50 if it was .50 or above it would round to 4 but it doesn't the same applies to 7.33 so
There were 72 more maple trees before the bug problem then after because there was 108 maple trees before the bug problem and 36 maple trees after the bug problem