Answer
$12x^\frac{17}{12}$
Work Step by Step
$$(3x^\frac{2}{3})(4x^\frac{3}{4})$$ $$=(3\times4)(x^\frac{2}{3} \times x^\frac{3}{4})$$
When two rational expressions with the same base are multiplied, add the exponents.
$$=12x^{\frac{2}{3} + \frac{3}{4}}$$
When adding fractions, you need a common denominator, in this case, 12:
$$=12x^{\frac{8}{12} + \frac{9}{12}}$$ $$=12x^\frac{17}{12}$$