Mathematics

Problem

Chantelle has completed this question. Can you spot any mistakes?

\begin{aligned} a^2 + b^2 &= c^2 \\ 5^2 + x^2 &= 13^2 \\ 10 + x^2 &= 26 \\ x^2 &= 16 \\ x &= 4\text{cm} \end{aligned}