## Basic College Mathematics (9th Edition)

$12$ mm
We know that for a right triangle the Pythagorean Theorem states: $leg_1^2+leg_2^2=hypotenuse^2$ $a^2+b^2=c^2$ Thus we have: $a^2+16^2=20^2$ $a^2+256=400$ $a^2=400-256$ $a^2=144$ $a=\sqrt{144}$ $a=12$ mm