The marked answer is correct. 
[tex] \frac{64}{343} [/tex]
rules for exponents:
[tex] a^{0} = 1 \\  a^{1} =a \\  a^{n} * a^{m} =  a^{n + m}  \\   a^{n} / a^{m} =  a^{n - m}  \\  a^{n} * b^{n} =  (a*b)^{n}  \\  a^{n} / b^{n} =  (a/b)^{n}  \\   (a^{n}) ^{m} =  a^{n*m}  \\  b^{-n} =  \frac{1}{ b^{n} } [/tex]
First step:
[tex] 6^{0} = 1[/tex]
Second step:
[tex]   ( \frac{2^{2}}{7^{1}} )  ^{3} =  \frac{ 2^{6} }{ 7^{3} } [/tex]
and
[tex] (1)^{3} =  1^{3} [/tex]
Last step:
[tex] 2^{6} *  1^3} = 64 * 1 = 64 \\  7^{3} = 343 \\  \\  \frac{2^{6} *  1^3}{7^{3}} = \frac{64}{343}  [/tex]