Answer
$reciprocals$.
Work Step by Step
Given any nonzero number/expression, the reciprocal of that number/expression is 1 over that number/expression.
Reciprocal of $\frac{2x}{7}$ = $\frac{1}{\frac{2x}{7}}$.
$\frac{1}{\frac{2x}{7}}$ = 1 $\div$ $\frac{2x}{7}$ = 1 $\times$ $\frac{7}{2x}$ = $\frac{7}{2x}$ .
