To simplify this, first, multiply the whole equation with x to get rid of the denominator.
[ x + 3/9/x + 12/6] * x
Simplify 12/6 beforehand, which is 2.
[ x + 3/9/x + 2] * x
Distribute x to each of the terms
x2 + 3/9 + 2x
This is already a simplified equation. If you wan to further simplify by getting rid of the fraction, multiply the whole equation with 9 to eliminate the denominator.
[x2 + 3/9 + 2x]*9
9x2 + 3 + 18x
9x2 + 18x + 3 =0