What is the value of x? round your answer to the nearest tenth if necessary.

right triangle whose two legs measure eight and x, and whose hypotenuse measures ten

This triangle is actually a 3-4-5 right triangle. By the Pythagoras Theorem, , we can see that  are the legs of the triangle, and  is the hypotenuse. Therefore, , and solving, we get . Therefore, 

This relates to Pythagorean Theorem. So you'd have to use a^2 + b^2 = c^2.
a & b are both "measurements" of x.
So you'd plug in 8 for a/b abecause (explained above this.).
And 10 would be in the place of c^2 because c = hypotenuse.

So it'd be a^2 + 8^2 = 10^2
a^2 + 64 = 100
-64 -64
a^2= 36
You'd have to square root the 36 because you're finding that one number and squaring it.So It'd turn out to being x=6.