Answer :
10 : 4 = 2.5
Then you need 2.5 more times cookies and brownies.
6 * 2.5 = 15 cookies
2 * 2.5 = 5 brownies
Then you need 2.5 more times cookies and brownies.
6 * 2.5 = 15 cookies
2 * 2.5 = 5 brownies