#### Answer

$\frac{343}{125}$

#### Work Step by Step

Step 1: $(\frac{25}{49})^{-\frac{3}{2}}$
Step 2: $(\frac{5^{2}}{7^{2}})^{-\frac{3}{2}}$
Step 3: $\frac{(5^{2})^{-\frac{3}{2}}}{(7^{2})^{-\frac{3}{2}}}$
Step 4: Simplifying the indexes, $\frac{5^{-3}}{7^{-3}}$
Step 5: Simplifying further, $\frac{7^{3}}{5^{3}}$ = $\frac{343}{125}$