Question 485840
Hey,

So for this problem we need to use the pythagorean theorem to discover what x is.
First, we need to plot the triangle that the two points are making:
First, the 8 and the 4 are the y measurements of the triangle, so if you subtract 4 from 8 you get 4. So we know that the measurement of the y leg is 4. 
Second, the pythagorean theorem says that      z^2 = x^2 + y^2 
We know what the z and the y are: z=5 and y=4. So if we plug them into the equation we get:
5^2 = x^2 + 4^2 => 25 = x^2 + 16 => 9 = x^2 => x = 3 
So if the x measurement is 3 then the x coordinate in the point must be 3 units away from (3,4) along the x axis. So the x coordinate is 3 + 3 = 6
Therefore, x = 6
It may be a little confusing but just plot out the triangle and use the pythagorean theorem, where the two short legs of the right triangle are the x and y and the long side, or the hypotenuse, is the z.
I hope this helps!