Having trouble using law of sines I have a triangle like this and I must find the length of the unkown side with question mark:



And I am using law of sines like this:

$$ \dfrac{\sin 55^\circ}{2} = \dfrac{\sin 35^\circ}{x} $$ 
then we got this equation 
$$ x = \dfrac{2\sin 35^\circ}{\sin 55^\circ} $$ 
and it gives me the answer $ x \approx 1.40 $

But when I use this equation: 

$$ \tan 35^\circ = \dfrac{x}{2} $$
$$ x = \dfrac{2}{\tan 35^\circ} $$

I get this answer: $ x \approx 2.85 $

Did I miss something?
You're last step is incorrect.

$$\tan 35^\circ = \frac{x}{2}$$

is equivalent to 

$$x = 2 \tan 35^\circ$$

which does give the same result.
You said:


  $$ \tan 35^\circ = \dfrac{x}{2} $$
  $$ x = \dfrac{2}{\tan 35^\circ} $$
  
  I get this answer: $ x \approx 2.85 $
  
  Did I miss something?


The answer is yes, you did.
$$ \tan 35^\circ = \dfrac{x}{2} $$
to remove the denominator, multiply both sides of the equation by the denominator thus:
$$ \frac 21 \times (\tan 35^\circ) = \frac 21 \times \biggr(\frac x2\biggr) $$
$$ 2 \tan 35^\circ =  x$$
$$ x \approx 2 \times 0.7002$$
$$x \approx 1.4004$$