#### Answer

5$\sqrt 3$

#### Work Step by Step

The Pythagorean Theorem says that $(leg_{1}) ^{2}$+$(leg_{2})^{2}$=$hypotenuse^{2}$.
This formula is more commonly referred to as $a^{2}$+$b^{2}$=$c^{2}$
You are given the lengths of one leg as 5 and the length of the hypotenuse as 10. Substitute 5 in for a and 10 in for c.
$a^{2}$+$b^{2}$=$c^{2}$
$5^{2}$+$b^{2}$=$10^{2}$
25+$b^{2}$=100
Subtract 25 from both sides.
$b^{2}$=75
Take the square root of both sides to find the length of the missing side.
b=5$\sqrt 3$