[tex]c] \ \frac{6+9\sqrt[3]5}{3}=\frac{3(2+3\sqrt[3]5)}{3}=2+3\sqrt35\\\\d] \ 2\sqrt[3]7+3\sqrt[3]7+4\sqrt[3]{-7}=5\sqrt[3]7-4\sqrt[3]7=\sqrt[3]7[/tex]
