Question

it took Marty 42 minutes to write a book report. then he spent 18 minutes correcting his report explain how you can use mental math to find out how long Marty spent on his book report

Answer 1

You simply add both times in your head to find the total of how long Marty spent on his book report.

Answer 2

So as of now you have two numbers . You break down the problem and in this situation they are asking us to add both numbers .. in total Marty spent 42+18 = 60 mins in total on his book report.