Helen the hippo and her friends are preparing for thanksgiving at Helen's house. Helen baked 36 cookies yesterday 4 cookies this morning and 35 cookies the day before yesterday. How many cookies did Helen bake till last night?
Helen baked 36 cookies yesterday. 
Then she baked 4 cookies this morning. 
That means she's baked a total of 40 cookies so far. 
But she also baked 35 cookies the day before yesterday. 

That means she's actually baked a total of 75 cookies.