cannot work this thing out ...
6400 bricks have been delivered to a site by the first day of a brick laying contract. subsequently 1600 bricks are delivered daily.
brick laying commences on the first day and proceeds regularly, the bricklayers using 2400 bricks per day.
write down two equations of the form of y=mx+c the first in respect of brick delivery, the second of bricklaying.
use these equations to find out how many days after the commencement of the contract the brick layers will have been run out of bricks.