12. Ellie wants to write a number in each box of the diagram shown. She has already written in two of the numbers. She wants the sum of all the numbers to be 35 , the sum of the numbers in the first three boxes to be 22 , and the sum of the numbers in the last three boxes to be 25 .

What is the product of the numbers she writes in the shaded boxes?
A 0
B 39
C 48
D 63
E 108
12. D Since the sum of the numbers in the first three boxes is to be 22 , the sum of the numbers in the last three boxes is to be 25 and the sum of the numbers in all five boxes is to be 35 , Ellie will write $(22+25-35)=12$ in the middle box. Therefore she will write $(22-3-12)=7$ in the second box and $(25-12-4)=9$ in the fourth box. Hence the product of the numbers in the shaded boxes is $7 \times 9=63$.