2/3:4/5

To simplify the ratio of \( \frac{2}{3} : \frac{4}{5} \), you can express it as a fraction:

\[ \frac{2/3}{4/5} \]

To divide by a fraction, you can multiply by its reciprocal:

\[ \frac{2}{3} \times \frac{5}{4} = \frac{2 \times 5}{3 \times 4} = \frac{10}{12} \]

Now, simplify \( \frac{10}{12} \) by dividing both the numerator and the denominator by their greatest common divisor, which is 2:

\[ \frac{10 \div 2}{12 \div 2} = \frac{5}{6} \]

Thus, the simplified ratio of \( \frac{2}{3} : \frac{4}{5} \) is \( 5:6 \).