Let's subtract 18 from 30 first. That means so far we will need 1.5 cups of raisins. We have 12 cookies left. You could do it 2 ways:
1. Percentage
12/18 = x/1.5
Cross multiply
18/18 = 1
You will need 1 cup of raisins.
2. Dividing
Half of 18 = 9
1.5 divide by 2 = .75
9 divide by 3 = 3
.75 divide by 3 = .25
3 x 4 = 12
.25 x 4 = 1
1 cup of raisins
The answer will be 2.5 cups of raisins.
1.5 + 1 = 2.5 cups of raisins
Hopes this helps :)
