Answer
$6\sqrt {5}-11x\sqrt[3] {5}$
Work Step by Step
$3\sqrt {20}-7x\sqrt[3] {40}+3\sqrt[3] {5x^{3}}$
=$3\sqrt {4\times5}-7x\sqrt[3] {8\times5}+3\sqrt[3] {5\times x^{3}}$
=$3\sqrt {2^{2}\times5}-7x\sqrt[3] {2^{3}\times5}+3\sqrt[3] {5\times x^{3}}$
=$3(2)\sqrt {5}-7x(2)\sqrt[3] {5}+3x\sqrt[3] {5}$
=$6\sqrt {5}-14x\sqrt[3] {5}+3x\sqrt[3] {5}$
=$6\sqrt {5}-11x\sqrt[3] {5}$
