Plz Help! NUmber 1 and 2! Brainlist for right answer!

Which simplifys to a+ b? a-(1-b)+1 -(1-a)-b+1 (a--1) -1)+1

Select the margin of error that corresponds to the sample mean that corresponds to each population: a population mean of 360, a standard deviation of 4, and a margin of error of 2.5%

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25