You actually have most of the answers correct.
E is the origin
D is the x axis
A is the y axis
B is at coordinates (1, 3)
C is at coordinates (3, 1)
*remember you go across on the graph x axis and then up y axis.
Either the amount of galleons or the galleys.
if given the amount of galleons, you can find the amount of galleys by dividing the number of given galleons by 5.
if given the amount of galleys, you can find the amount of galleons by multiplying the number of given galleys by 5.
4 * (25 * 1.2) = (4 * 25) * 1.2
4 trays are needed because your number is 3.75 and you need another tray for the rest