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

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

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.

1. isolate the variable, in this case, d. subtract 35.5 on both sides of the equation.2. 52 subtracted by 35.5 is 16.53. therefore your answer would be d= 16.5this is the basics of pre algebra, isolating variable through adding, subtracting, multiplying, and dividing, if you have any other questions to ask just comment!