How to extend this activity;-
Think about having the same number of buttons on each of the 3 snowmen. Can you write this as a number sentence?
Now arrange the buttons so there are different amounts on each snow man and write the number sentence for how you have chosen to arrange them.
Use 7 buttons. Can you arrange them so the 3 snowmen have the same number of buttons? If not, how many more buttons do you need or how many would you need to take away?