Ok so first we need to work out the vertical line in the middle (ab) using Pythagoras 
Square root(7.5^2+4.9^2) to get 8.958794562
Now we know the length of the line ab so we can work out x using trigonometry 
Since line ab is opposite the angle and x is adjacent (or not the hypotenuse the slope) the tan rule is used which is tan(0)=o/a
So tan(55.8)=8.9587../a
        *a.                *a
         /tan(55.8).      /tan(55.8)
a=8.9587../tan(55.8)
a=6.088390497
a=6.09
x=6.09