how do I do this:

given g(x)= x^2/3x+2 determine any x values for which f(x)=1/2.
I really don't understand what to do.

Since they give you g(x) and talk about f(x), the problem makes no sense.

They might have meant f(x) and g(x) to mean the same function.

In that case, solve the equation

x^2/(3x+2) = 1/2

x^2 - (3/2)x - 1 = 0
There are two possible real solutions. Use the quadratic equation to get them.