Can some one me with this im having trouble. ?

So 12=total
7=blue
black=total-blue=12-7=5
black=5

1. 2/3 of 12 were taken out or 24/3 were taken out or 8 marbles were taken out
   there is not enough info becasue it doesn't specify which ones were taken out

2. there is not enough info

3. not chosen=total-chosen=12-8=4 so 4 were chosen