Jenny buys 1 bag of cookies a week.  The bag has 36 cookies and she puts 4 cookies in her son's lunch box 5 days a week.  Her husband eats 1 cookie a day for 7 days.  Jenny eats the rest of the cookies.  How many cookies does Jenny eat?
Work out the solution step by step. 
The son gets 4 cookies a day for 5 days so he eats 4*5 = 20 cookies
Her husband eats 1 cookie a day for 7 days so he eats 1*7 = 7 cookies
There are 36 cookies in a bag and her son eats 20 and her husband eats 7 so Jenny eats 36-20-7 = 9 cookies