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

Isolate the square root on the left and clear the denominator on the right hand side by multiplying the 3 that turns up:

3sqrt(2x/3) = (2x-12)/3

-> 9sqrt(2x/3) = 2x-12

now we can square both sides:

81*2x/3 = 4*(x-6)² = 4*(x²-12x+36) = 4x²-48x+144

Collect and put into the form ax^2 + bx + c = 0 which can then be solved in any way you like

4x² - 102x + 144 = 0