one way is just to recognize that
2.88=12 cookies
konw that
12/6=2
so divide both sides by 6
0.48=2 cookies
2 cookies is 48 cents
ratio and proportaion way
cost:cookies=2.88:12
cost of 2 cookies is x
2.88/12=x/2
times both sides by 12
2.88=6x
divide both sides by 6
0.48=x
the cost is 2 cookies is $0.48 or 48 cents