For $\ce{CO (g) + H2 (g) <=> CH2O (g)}$
with Kc = 0.068 @ 273K
initial concentrations being $\ce{[CO]}$ = 1.25M, $\ce{[H2]}$ = 2.00M, $\ce{[CH2O]}$ = 1.00M
I did $\frac{1.00}{((1.25)(2.00)} = 0.4$, which is more then Kc, so it's leaning to the left, will produce more reactants, and products will lower. So the I did:
$\frac{1.00 - x}{(1.25 + x)(2.00 + x)} = 0.068$
Multiplied the bottom and got $X^2 + 3.25x + 2.5$
so
$\frac{1.00 - x}{X^2 + 3.25x + 2.5} = 0.068$
I then tried multiplying the denominator by 0.068 and rearranging to solve for $x$ from there, but that's where I got stuck. $X$ is supposed to be 0.65.