Carol puts some green cubes and red cubes in a box. The ratio is 2:1. She adds 12 more cubes to the red cubes in the box and the ratio becomes 4:5. How many green cubes were in the box?

16 green cubes are in the box.

Step-by-step explanation:

No. of red cubes at first (x):

4 (x + 12) = 5 (2x)

4x + 48 = 10x

6x = 48

x = 8

No. of green cubes:

= 8 * 2

= 16

Answer: 16 green cubes are in the box.

20 red cubes are in the box in the end.

Proof (the ratio in the end is 4:5):

= 16 is to 20

= 16/4 is to 20/4

= 4 is to 5