Answer:
In favor: 4/10 or 40%, Odds Against: 6/10 or 60%
Explanation:
Since there are 10 "slices" we can assume that each one has a 10% chance of getting spun on. Since there are 4 grey slices that give Melissa a prize, she has a 4*10 percent chance, or a 40% chance of getting a gift card.
The remainder, 100% - 40% = 60%, she has a 60% chance of not-winning a gift card.
Hope this helps!
:)