Evelyn wants to buy a dictionary that costs $9, a dinosaur book that costs $18, and a children's cookbook that costs $12. She has saved $30 from her allowance. How much more money does Evelyn need to buy all three books?

First, you have to add 9, 18, and 12. When we add this we get 39. She has 30 dollars, do we can see that she needs $9 more to get all three books.

Step-by-step explanation:

step-by-step explanation:

you can add the two numbers and divide the result by 2. or you can find the gap between the two numbers and add half of this to the smaller number.