Carol was sending out birthday invitations to 44 friends. She bought 11 packs each one having the same number of invitations. How many invitations are in each pack?
Carol is sending out 44 invitations. 
She bought 11 packs. 
Each pack has the same number of invitations. 

That means that the total number of invitations is 44, and she bought them in 11 packs. So we can set up the equation: 

44 = 11x

We can solve this equation for x, which is the number of invitations in each pack. 

44/11 = x

4 = x