The area of the green sector is 22.33646, you can shorten that down to 22.34 if you would like. But this is the correct answer. :)
(My Work: Area of a Circle= pi(r)^2 so I took your radius provided and plugged it in. pi(3)^2=28.274... and since you have 75 degrees cut out, I multiplied by .21 since 75/360=.21. I took that answer and subtracted it from our original (28.274) to get the final answer: 22.34)
Hope this helped and wasn't to confusing!