15+21=

37+42=

There are 34 ghouls and 25 dragons.
How many monsters are there in all?

I invited 48 mummies and 27 ghosts to my Halloween party. How many mummies and ghosts did I invite in all?

35 trick-or-treaters came to my door dressed as princesses. 62 trick-or-treaters came to my door dressed as knights. How many princesses and knights trick-or-treated at my door?