The pythagorean theorem states that a² + b² = c².
We have a = 10 and c = 20.
100 + b² = 400
Subtract 100 from each side.
b² = 300
Get the square root of 300.
It could be expressed as b ≈ 17.321, or could stay in radical form as[tex] \sqrt{300} [/tex].
Hope this helps!