Two is thirty-one, divided by the sum of a number and four. find the number.

I’ve been trying all day to figure this puzzle out. i need the work for it aswell. it is a factoring polynomials tarsia. the image is below.

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?

Arectangle plot measure 20ft. by 30ft. a 3-ft.-wide sidewalk surrounds it.find the area of the sidewalk.