Since the triangle rectangle has an angle of 45 degrees and a side of 8, then the other side must be also 8 and the other angle must be also 45 degrees
Perimeter = 27.31 = 8 + 8 + hypotenuse
Solving for hypotenuse:
Hypotenuse = 27.31 - 8 - 8 = 11.31
Answer:
Hypotenuse = 11.31