pls help me with this multiple choice !

Answer:
A
Step-by-step explanation:
since the angles are 45,45 the triangle is an Equilateral triangle
V=12
[tex] {u}^{2} = {12}^{2} + {12}^{2} \\ {u}^{2} = 288 \\ u = \sqrt{288} = 12 \sqrt{2} [/tex]