HELP ME PLEASE I NEED THIS and tell me how to solve for it

Answer:
616.6 square cm
Step-by-step explanation:
Area of a regular octagon
[tex] = 2 {a}^{2} (1 + \sqrt{2} ) \\ = 2 \times {12}^{2} (1 + 1.414) \\ = 2 \times 144 \times 2.141 \\ = 288 \times 2.141 \\ = 616.608 \\ = 616.6 \: {cm}^{2} [/tex]