adam read a 360 page book in 3 days. he read twice as many pages on the middle day as he did on the first day or last day. How many pages did he read on the LAST day.
Let x stand for what was read the first day and the last day, then 2x = what was read the middle day.
x + 2x + x = 360
4x = 360
Divide both sides by 4.