Question

This is the question

Answer 1

Using pythagorean theorem:

$\begin{gathered} c^2=a^2+b^2 \\ a=\sqrt[]{c^2-b^2} \\ a=\sqrt[]{25^2-17^2} \\ a=\sqrt[]{336} \\ a=4\sqrt[]{21}\approx18.3 \end{gathered}$