Simplify the expression x2/7y2/3(x1/8y1/6)1/7x3/4y2/7\displaystyle \frac{{{x}^{{-{2}/{7}}}{y}^{{-{2}/{3}}}{\left({x}^{{{1}/{8}}}{y}^{{-{1}/{6}}}\right)}^{{-{1}/{7}}}}}{{{x}^{{{3}/{4}}}{y}^{{-{2}/{7}}}}}. Write your answer in rational exponent form,using nonnegative exponents.