Geometry assistance needed, thank so much

Answer:
7√2 / 2
Step-by-step explanation:
An isosceles right triangle is also known as a 45-45-90 triangle. For such a triangle, the hypotenuse (long side) is √2 the legs.
s√2 = 7
s = 7/√2
s = 7√2 / 2
You can also show this with Pythagorean theorem.