Is there a direct proportion in 3y=1/2x? if there is one, what is the constant of proportionality?

Yes, there is.

Just divide 3 to both sides:

y = (1/2 / 3) x

Find the reciprocal of 3 and multiply:

y = (1/2 * 1/3) x

Multiply the numerators and denominators together:

y = 1/6x

So the constant of proportionality is 1/6.

A direct proportion is any equation where y = mx+b. (i. e., a linear equation)

Each side of 3y = 1/2x can be divided by 3 to get y = 1/6x, satisfying the condition of y = mx+b. (b=0)

In this case, the constant of proportionality would be 1/6.