c) $\sqrt[]{81}$ + 4$\sqrt[]{5^{2}}$ = 9 + 4.5 = 9+20=29
d) $\sqrt[]{2}$ . $\sqrt[]{18}$ - $\sqrt[]{64}$ : $\sqrt[]{9}$
= $\sqrt[]{2}$ . 3$\sqrt[]{2}$ - 8 : 3
= 6 - $\frac{8}{3}$ = $\frac{10}{3}$
e) $\sqrt[]{(\sqrt[]7-3){}^{2}}$ + $\sqrt[]{(\sqrt[]{7}+1) ^{2}}$
= 9 - $\sqrt[]{7}$ + $\sqrt[]{7}$ + 1
= 10
f) $\frac{2}{\sqrt[]{2}+1}$ - $\frac{2}{\sqrt[]{2} -1}$
= $\frac{2\sqrt[]{2} -2-2\sqrt[]{2}-2}{2-1}$
= $\frac{-4}{1}$
= -4
