Answer :
Is it asking how many she began with before she sold them? If so, then I think at the beginning she started out with 40. I think she had 40 because she sold half, and when you divide 40 by 2 it divides perfectly giving you 20. Then add 16 to that and you come out with 36.
x= comic books
1/2 x+16=32
multiply by 2 to eliminate the fraction
x+ 32=72
subtract 32 from both sides
x= 40
Jill began with 40 books
hope this helps