Use the Pythagoras Theorem in the corresponding right angled triangles.
Add all the sides up to equal 30 in an equation because you are given the perimeter. The perimeter is the length around a two dimensional shape. This means the perimeter is the length of all the side lengths added together.
(x) + (2x + 2) + (13) = 30
Combine like terms.
3x + 15 = 30
Subtract 15 from both sides.
3x = 15
Divide both sides by 3.

180
This is because 12x5x3 = 180