Question 255720
To solve this problem, you need to remember that the diagonal of a rectangle splits it into two right triangles.  So to find the length of the diagonal we only need to use Pythagorean's theorem.

{{{5^2 + 12^2 = d^2}}}
{{{25 + 144 = d^2}}}
{{{169 = d^2}}}
{{{13 = d}}}