Answer
a)$8\sqrt 5$
b)$\sqrt[3] 2$
Work Step by Step
a)$\sqrt {125}+\sqrt {45}=\sqrt {25}\sqrt 5+\sqrt 9\sqrt 5=5\sqrt 5+3\sqrt 5=8\sqrt 5$
b)$\sqrt[3] {54}-\sqrt[3] {16}=\sqrt[3] {27}\sqrt[3] 2-\sqrt[3] 8\sqrt[3] 2=3\sqrt[3] 2-2\sqrt[3] 2=\sqrt[3] 2$
