Answer
$x^{5/4}y^{2/3}z^{5/7}$ and $x^{1/2}y^{2/3}z^{5/7}$
Work Step by Step
In order to find two expressions with noninteger exponents whose quotient is $x^{3/4}$, we first look for two rational numbers (not integers) whose difference is $3/4$. For example:
$$\dfrac{5}{4}-\dfrac{2}{4}=\dfrac{3}{4}.$$
So $\frac{5}{4}$ and $\frac{2}{4}=\frac{1}{2}$ will be the exponents of $x$.
We can add other variables to our expressions, but they must have equal exponents.
For example:
$$x^{5/4}y^{2/3}z^{5/7}\text{ and }x^{1/2}y^{2/3}z^{5/7}.$$
Check the quotient:
$$\dfrac{x^{5/4}y^{2/3}z^{5/7}}{x^{1/2}y^{2/3}z^{5/7}}=x^{5/4-1/2}y^{2/3-2/3}z^{5/7-5/7}=x^{3/4}\checkmark$$
