Answer: B) [tex]\frac{10}{\sqrt{2}}[/tex]
For any isosceles right triangle (aka 45-45-90 triangle), the hypotenuse is always equal to sqrt(2) times the leg. If x is the leg and y is the hypotenuse, then
[tex]y = x*\sqrt{2}[/tex]
which solves to
[tex]x = \frac{y}{\sqrt{2}}[/tex]
from here we plug in the given hypotenuse y = 10 to get the final answer. Optionally we could rationalize the denominator, but your teacher has chosen not to.
