The fourth one since it will pass the vertical test.
The answer is 12 because (a^2 + b^2 = c^2)
5^2 + b^2 = 13^2
25 + b^2 = 169
169- 25 = 144

Sqaure root of 144 is 12 so If we plug that in..
25 + 144 = 169
5^2 + 12^2 =13^2
This all checks out
~Hope This helps
4/5. I was doing math assignments like this earlier and remember how to do this. If you need more help on this let me know.
Answer: 84
<u>Step-by-step explanation:</u>
Set up a proportion as follows: 

Cross multiply: 12x = 7 × 144
Divide by 12: x = 7 × 12
Simplify: x = 84