Karen buys 8.5ounds of flour. she uses 2.5 pounds to bake bread. she keeps the rest of the flour in small storage baga. if each storage bag contains 2/5 pound of flour, how many storage bags does she use?

Karen bought 8.5 pounds of flour. She uses only 2.5 pounds of flour to make the bread.
So, the amount of flour left after baking the bread = (8.5 - 2.5) pounds
                                                                                = 6 pounds
So 6 pounds of flour is left. She breaks this 6 pounds of flour into several bags and each bag contains 2/5 pound of flour.
Now to calculate the 2/5 th pound of flour in decimal, we get = 0.4 pounds
So each of the bags contain 0.4 pounds of flour. Now we have to calculate the number of bags in which the flour have been kept.
So,
Number of bags required = 6/0.4
                                         = 15
So 15 small storage bags are required by Karen to keep the remaining flour.

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.