The side on the front of 30° is 1/2 of hypytenuse
Then 1/2 of 4=2 and the ather side with theorem of pytagore is squares root of(4^2-2^2)=sq .root of 12
This side(square root of 12) is 1/2 of hypotenuse then
Hypotenuse is 2*square root 12
X^2=(2*sq .root12)^2 -(square root 12)^2
X^2=48-12=36
X=6