The angle markings at the bottom of the triangle mean they are congruent. Since they are the only two congruent to each other, that means this triangle is an isosceles triangle.
In an isosceles triangle, not only are the bottom angles congruent, their opposing sides are congruent as well. In this instance, that means 9x - 8 = 28. Knowing that we can solve for x.
Each is 7 long and the whole piece is 56 so we can make 8 down the length and each is 1 wide and the whole things is 3 so that makes 3 across. we multiply these to get 8*3= 24