The answer would be one and a half for each friend.
1. You need to make a proportion
2. Your proportion would be 8 over 10 equals X over 15
3. Your equation would be 10x=15(8)
4. 15x8=125
5. 10x=125
6. you would divide 125 by 10
7. thats your answer
Answer is in the file below
tinyurl.com/wpazsebu