I can use a little help please

Answer:
The missing side's length is 18.2
Step-by-step explanation: To find a missing side in a right triangle, you use the Pythagorean theorem to solve it. According to the Pythagorean Theorem, [tex]12.6^{2}[/tex] + [tex]13.1^2[/tex] = [tex]x^{2}[/tex], so 158.76 + 171.61 = [tex]x^{2}[/tex] ⇒ 330.37 = [tex]x^{2}[/tex] ⇒ x ≈ 18.2.