This triangle is a 30-60-90 triangle, which you can just find by solving for the unknown angle in the triangle, making it a 30-60-90 triangle.
You'll need to memorize the side lengths for these triangles, but the side opposite from the hypotenuse (x in this case), will be half the length of the hypotenuse.
Meaning that [tex]2x=8[/tex]
So [tex]x=4[/tex]
Hope this helps.
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