### Instruction: Multiply $\frac{2}{3}$ by $\frac{4}{7}$.### Response: To multiply two fractions, I can multiply the numerators and multiply the denominators.
The numerator of the product will be $2 \times 4 = 8$.
The denominator of the product will be $3 \times 7 = 21$.
So the product is $\frac{8}{21}$.