Answer:
12
Step-by-step explanation:
The Pythagorean Theorem says that in a right triangle, [tex](\text{leg})^2+(\text{leg})^2=(\text{hypotenuse})^2[/tex], so in this triangle, the legs are 5 and a; the hypotenuse is 13.
[tex]5^2+a^2=13^2\\25+a^2=169\\a^2=144\\a=\sqrt{144}\\a=12[/tex]
