Let's say that X is what the other 5 siblings pay. X + $9.50 is what Chetan pays. X + $9.50 is 1/5 of the cost of the present. To solve this we have to do 0.8 divided by 5 (the remaining cost split between 5 people) which is 0.16. Now from this we can learn that $9.50 is 0.04 of the cost of the present. A simple way to solve this is do 1.00 divided by 0.04 and then multiply $9.50 by that amount. 1.00 divided by 0.04 is 25 so $9.50 times 25 is $237.5.
The present costs $237.5
As I read over this I may not be correct, however this is how I solved it as an advanced mathematics grade 8 student.