Question

Sqrt(15)/5 *sqrt(20)

Answer 1

So if you mean: $\frac{ \sqrt{15} }{5}$ times $\sqrt{20}$ then
simplify
rememeber
$x^{ \frac{m}{n} }= \sqrt[n]{ x^{m} }$
and
$[x^{n}]^{m}= x^{nm}$
and
$\sqrt{x} \sqrt{y}= \sqrt{xy}$

multiply

$\frac{ \sqrt{15} }{5}$ times $\frac{ \sqrt{20} }{1}$=$\frac{ \sqrt{300}}{5}$

simplify √300
√300=√3 times √100
we know that √100=10 so
√300=√3 times 10
therefor
$\frac{ \sqrt{300} }{5}$ = $\frac{10\sqrt{3}}{5}$= $\frac{5}{5}$ times  $\frac{2\sqrt{3}}{1}$ = 1 times $\frac{2\sqrt{3}}{1}$=2√3

Answer 2

So,

$\frac{ \sqrt{15}}{5} * \sqrt{20}$

Simplify the square root of 20.
$\sqrt{20} = \sqrt{4} * \sqrt{5} = 2 * \sqrt{5} = 2 \sqrt{5}$

$\frac{ \sqrt{15}}{5} * \frac{ 2\sqrt{5} }{1}$

Multiply.
$\frac{ 2\sqrt{75}}{5}$

Simplify.
$\frac{ 2\sqrt{25}* \sqrt{3} }{5}$
$\frac{ 2 * 5* \sqrt{3} }{5}$
$\frac{10\sqrt{3} }{5}$
$\frac{2\sqrt{3} }{1}$
$2\sqrt{3}$