Im bad with shapes just look at the picture and tell me best of luck

They are both right triangles so you can use the Pythagorean Theorem to get the length of the missing side

12^2 = 144. 5^2 = 25. 144 + 25 = 169. 13^2 = 169. Or you could say the sure root of 169 is 13.

Step-by-step explanation:

The triangles are congruent because the three sides of triangle A are equal to the three sides of triangle B.

In geometry they call that proof "sss" meaning 3 same sides. Or you could prove by "sas" 2 equal sides and an equal angle.