[tex]a) \\ ( - 3) {}^{4} \\ 3 {}^{4} \\\boxed{\boxed{\boxed{81}}} \\ [/tex]

[tex]b) \\ ( \frac{2}{7} ) {}^{ - 3} \\ ( \frac{7}{2} ) {}^{3} \\ \frac{7 {}^{3} }{2 {}^{3} } \\ \frac{343}{8} \\ \boxed{\boxed{\boxed{42,875}}} \\ [/tex]

[tex]c) \\ 25 {}^{ \frac{1}{2} } \\ (5 {}^{2} ) {}^{ \frac{1}{2} } \\ 5 {}^{2 \: . \: \frac{1}{2} } \\ 5 {}^{1} \\\boxed{\boxed{\boxed{5}}} \\ [/tex]

atte. yrz