Respuesta :

12 - 3 = 9
So there are 9/12 cookies left. 
So then John ate 3/12 cookies. 
3/12 = 1/4 
Convert into a decimal. .
1/4 = 0.25
0.25 = 25%
So, James bought 12 cookies and ate 3 of them. He ate 25% of the cookies.