Simplify the Numerical Expression $\left( \frac { 2 ^ { - 1 } } { 7 ^ { - 2 } } \right) ^ { - 1 }$

Short Answer

Simplify the numerical expression. $\left( \frac { 2 ^ { - 1 } } { 7 ^ { - 2 } } \right) ^ { - 1 }$ Please enter your answer as a fraction.