#### Answer

$\frac{3(x+7y)}{4x(2x-y)}$

#### Work Step by Step

We factor the expressions in both the numerator and denominator in order to cancel out common factors in the numerator and the denominator:
$\frac{6x^{2}+42xy}{16x^{3}-8x^{2}y}$
=$\frac{2x(3x+21y)}{2x(8x^{2}-4xy)}$
=$\frac{(3x+21y)}{(8x^{2}-4xy)}$
=$\frac{3(x+7y)}{4x(2x-y)}$