The steps are labeled, and the chart on the side is to help you know which numbers are x, and which ones are y.
2 hours = 120 minutes
120/30 = 4
1/4 of 2 hours is 30 minutes.
Its 15 boats bcuz...252+288=540 and 540/36= 15 boats :D
X = y + 5
-y + x - x = y - y + x + 5
-y = x + 5
y = x - 5