Answer:
5
Explanation:
By using the Pythagorean theorem, you can solve for x
a^2 + b^2 = c^2
Where in this scenario a = 12 and c = 13.
B isn't known, so you use the other bits of information in the Pythagorean theorem, which will give you 5
12^2 + 5^2 = 13^2
169 = 169