12 (56) 16 17( )21 Please answer as soon as possible

12 (56) 16 17( )21 Please answer as soon as possible

16-12 = 4; take the average 14 of 12 and 16, and multiply by 4 to get 56
21-17 = 4; take the average of 17 and 21, 19, and multiply by 4 to get 76