Paco had w cookies. He gave x cookies to his friend and ate y cookies. How many cookies did Paco have left?
Paco had w cookies. He gave x cookies to his friend and ate y cookies. 

Paco had 36 cookies. He gave 14 cookies to his friend and ate 10 cookies. 

Paco had 36 - 14 - 10 = 12 cookies left.