Try to understand the model. Since after giving 23 away and using 5/9 of the remaining, that means the left over 4/9 after giving 23 is 2/5 of total stickers John had. Since 4/9 of the remaining is 2/5, means the other 4/9 part of the 5/9 used is also 2/5 of all John has. This leaves us with 1/5 or total which is made up of the 23 and 1/9 of remaining after giving away 23. Since 2/5 of total is 4/9 of remaining after giving away 23, that means 1/5 must be 2/9 of remaining after giving away 23. Remember 1/5 we found out was also 23 and 1/9 of remaining? That means 1/9 of remaining must be 23! So we just take 23 times 10 since we have 10 units !