Mr shea saved 2500 dollars in april. his monthly salary is twice the amount he saved in april. in may he saved a certain amount of money. he spent 4200 dollars more than the amount he saved. how much did he save in may?

He saved 2500 in April.
His monthly salary is twice that saved in April = 2 * 2500 = 5000

Let the amount saved in May = m
Amount spent in May =  4200+ m

For the Month of May: 
Monthly Salary - Amount Spent = Amount Saved.
5000 - (4200 + m) = m
5000 -4200 - m = m
800 = m + m
800 = 2m
800/2 = m
400 = m
Amount saved in May = 400 dollars.