Trigonometry, i don’t know how to find x.

Step-by-step explanation:

I still suspect that Angle A is 30° and Angle B is 60°.  Otherwise the labels do not fit the illustration.

If Angle A is 60°, as you insist, then the solution (the length of x) is as follows:

                          opp side        x

tan 60° = √3 = =

                          adj side          7

Then:

   √3            x

 =  

     1              7

Thru cross-multiplication we see that x = 7√3

Multiply both sides by 7, which produces:

7√3 = x