Divide the figure into a triangle on the left and a rectangle on the right. You know the side lengths of the rectangle are 3 x 10, so multiply to get the area of the rectangle. Next, find the area of the triangle. The area of a triangle is given by 1/2bh, where b is the base and h is the height. Because you know the short side of the rectangle is 3, subtract 3 from 5 to get the base of the triangle. then multiply that by 10, the height, and divide by 2 to get the area of the triangle. Then just add up the area of the triangle and the area of the rectangle to get your answer :)