Answer
$\sqrt{5}/4$
Work Step by Step
When taking a square root of a fraction, we take the square root of the numerator (top of the fraction) and denominator (bottom of the fraction) separately. The square root of 64 is 8, and there is no integer square root of 20, giving us the expression of $\sqrt{20}/8$. However, we know that 4, which is a perfect square, is a factor of 20. Thus, we can simplify:
$\sqrt{4}\sqrt{5}/8=2\sqrt{5}/8=\sqrt{5}/4$
