Set up a proportion: 3/10= x/80. Then if you multiply 10 by 8, you get 80 on both sides, But, If you do it to the top, you also have to do it to the bottom, so the anser is 3 x 8 , or 24.
The unknowns should be 1 or 3. we don't know the total number of children and parents in the room, but we have a clue which 25, so if we were to subtract 9 from 25 we would get 16. i would recommend number 1
