The ratio of red jelly beans to yellow is 3:4. If greg eats 3 red and 6 yellow, the ratio is 4:5. How many yellow jelly beans were originally in the dish?

Red = X

Yellow = Y

X:Y = 3:4

X-3: Y-6 = 4:5

1. 3Y = 4X - > Y = 4/3X

2. 4 * (Y-6) = 5 * (X-3)

3. 4Y - 24 = 5X - 15

4. 4*4/3X - 24 = 5X - 15

5. 16/3X - 24 = 5X - 15

6. 16X - 72 = 15X - 45

7. X = 27. So, Y = 36