Answer:
11 is 405, 12 is 107.5, 13 im not sure of
Step-by-step explanation:
First on 11 you can just do 21*21 (the big square) and subtract that by 36 (which is 6*6, the small square), you'll get 107.5.
Then on 12, it is made up of a large rectangle, a small triangle, and a flatter triangle. The top triangle's formula is 1/2(7*3) which = 10.5. The big rectangle is 13*7 = 91. The last triangle is 1/2(4*3) which = 6. It is 3 because 13-10. Add all those up and you should get 107.5.
And I just want to know on number 13 if that 11 is the radius or diameter. I can't seem to tell.
