Answer: 672
1. You need to find the arena of the missing piece so with the 40 on top you will subtract 12 which will give you 28
2. To find the other side subtract 28-12 to get 16 then you will multiple then together to get 448
3. Now just Multiply 40 and 28 to get 1120
4. Subtract 1120 and 448 and you’ll get the answer of 672