A car travels a distance of 210 miles in a time of 3.2 hours. What is its average speed rounded to 1dp?

One unique triangle, because those angles add up to 180, and that's how many degrees there are in one triangle.

Use pythagorean’s theorem and find the missing side lengths of the two smaller triangles and add them together
13^2 - 12^2 = 5
15^2 - 12^2 = 9
5+9 = 14
14 is the length of each side of the square
14^2 + 14^2 = 19.8
19.8 is the diagonal length of the inside if the square

Use that as an example to solve it