Look at the graph here : https://www.desmos.com/calculator/e3xiqeprcw
The total area of the region = 3 * 6 = 18
The graph of the inequality x + y ≤ 5 forms a trapezoid with bases of 5 and 2 and a height of 3
The area of this trapezoid = (1/2) (3) ( 5 + 2) = 21/2 = 10.5
So.....the probability that a point falls into the trapezoid = 10.5 / 18 = 7/12
