So for this, we will be using the pythagorean theorem, which is [tex]leg^2+leg^2=hypotenuse^2[/tex] . 9 is being used instead of 18 because we are using only one half of this triangle.
Firstly, apply the numbers to their place [tex]9^2+20^2=x^2[/tex]
Solve the exponents to get [tex]81+400=x^2[/tex]
Add up the left half of the equation to get [tex]481=x^2[/tex]
And lastly, square root both sides of the equation, and your answer should be [tex]21.9=x[/tex]
