To find the constant of proportionality given the points \((\frac{2}{3}, \frac{3}{4})\), we can use the formula:
\[ k = \frac{y}{x} \]
where \(k\) is the constant of proportionality, \(y\) is the second value of the point, and \(x\) is the first value of the point.
Using the values from the point:
\[ x = \frac{2}{3} \] \[ y = \frac{3}{4} \]
Now, we can substitute these values into the formula:
\[ k = \frac{\frac{3}{4}}{\frac{2}{3}} \]
To divide fractions, we multiply by the reciprocal of the divisor:
\[ k = \frac{3}{4} \times \frac{3}{2} = \frac{3 \times 3}{4 \times 2} = \frac{9}{8} \]
Thus, the constant of proportionality is:
\[ \frac{9}{8} \]
This is already in simplified form.
So, the answer is:
\[ \text{Constant of proportionality: } \frac{9}{8} \]