Afruit salad recipe requires 20 cups of blueberries, 22 cups of strawberries, and 18 cups of grapes. to make a batch with 3 cups of grapes, how many cups of berries are needed in all?

The ratio is b:s:g=20:22:18  and if we only care about berries and grapes the ratio is:

b:g=42:18 now we can set up a relationship to solve...

3g(42b/18g)=7b

So using 3 cups of grapes requires 7 cups of berries in total.  

Figure it out your self