Leon has 3 cards. Each of the cards has a different whole number on it. When he adds the 3 numbers, he gets 15. When he multiplies the 3 numbers, he gets 72. What is the difference between the greatest and smallest numbers on the cards?
so, let the numbers be x,y,z. Then you know that
x+y+z = 15
xyz = 72
What are the factors of 72?
1,2,3,4,6,8,9,72
Which three of these add up to 15?
Looks like
1+6+8 = 15
2+4+9 = 15
3+4+8 = 15
Looks like there's more than one answer possible, eh?