This kinda easy. Every 3 yellow drops is 4 blue drops, so here's the answer. 3 = 4, 6 = 8, 9 = 12, 12 = 16. so you would need 16 blue drops.
Answer:
The original number is 17.
Step-by-step explanation:

The standard equation of an ellipse is:
(x-h)²/a² + (y-k)²/b² = 1
Since the center at the origin, then h = k = 0
The height of this ellipse = 8 units and the width = 4 units, that means the major axis is b (=8) and the minor axis is a (=4)
Then the equation becomes:
x²/16 + y²/64 = 1