Step-by-step explanation:
The numbers in the box share something in common called AC method.
The two number that is missing must add to get the bottom number while must be a factor of the top number.
For example number 1
The factor of 12 are positive and negative 1,2,3,4,6,12
We can use positve 6 and 2 because 6+2=8
Another example is no.2 the factor of -9 are negative and positve 1,3,9. We can 3 and -3 since they multiply to -9 and add to 0.
