The pythagorean theorem states that a^2+b^2=c^2. a and b are the shorter sides and c is the hypotenuse, or the longest side. You can tell the hypotenuse because it is opposite to the right angle.
Therefore, a=6, b=8 and c=x. You can switch a and b if you like, it doesn't really matter.
using the pythagorean thm. 6^2+8^2=x^2. You simplify the exponents and combine like terms to get x^2=100. You take the square root of both sides and get 10.
