Can anyone answer this and the step by step process?

x=6
Step-by-step explanation:
using Pythagoras theorem
on small triangle
(2)^2 + b^2 = (√13)^2
4 + b^2. = 13
b^2 = 13- 4
b^2 = 9
b = 3
so x = 2× b
= 2×3
=6