Answer
$2\sqrt 5-5\sqrt 3+5\sqrt 7$
Work Step by Step
$\sqrt 20-\sqrt 75+5\sqrt 7=\sqrt (4\times5)-\sqrt (25\times3)+5\sqrt 7=(\sqrt 4\times\sqrt 5)-(\sqrt 25\times\sqrt3)+5\sqrt 7=2\sqrt 5-5\sqrt 3+5\sqrt 7$
We know that $\sqrt 4=2$, because $2^{2}=4$.
We know that $\sqrt 25=5$, because $5^{2}=15$.
