The answer is 4
To get this answer, we'll first need to find the length of segment ST. This is the short leg of the 30-60-90 triangle on the left. The short leg and the long leg tie together with this formula
long leg = (short leg)*sqrt(3)
Since the long leg is equal to 2*sqrt(3), this means that the short leg must be 2 units long.
The hypotenuse of the same triangle is TR = 4 which is double that of the short leg.
Moving onto the other triangle, which is 45-45-90, the x is the other leg. Recall that for 45-45-90 triangles, the two legs are congruent or the same length. So,
TR = RQ = 4
which is why x = 4