You have the following algebraic equation:
1/3x = 1/3 + 6/x
In order to solve the previous equation you first multiply both sides of the equation by x, thus, you can quit x denominators in the equation. Proceed as follow:
1/3x = 1/3 + 6/x multiply by x both sides
1/3 = x/3 + 6 multiply by 3 both sides
1 = x + 18 subtract 18 both sides
1 - 18 = x + 18 - 18
-17 = x
-17 = x is the same as x = -17. The solution to the given equation is x = -17.