Archie has 13 post-it notes more than Fiona. How many post-it notes must Fiona get from Archie so that she has 19 post-it notes more than him?

	Archie	Fiona
Comparing Archie and Fiona at first	13 more
Before
Change	- ?	+ ?
After
Comparing Archie and Fiona in the end		19 more

If Archie gives 13 post-it notes to Fiona, she will have 13 more post-it notes than him. However, Fiona must have 19 more post-it notes than Archie in the end. So, Archie has to give Fiona more post-it notes.

Number of more post-it notes that Archie has to give to Fiona
= (19 - 13) ÷ 2
= 6 ÷ 2
= 3

So after giving 13 post-it notes to Fiona, Archie has to give her another 3 more post-it notes so that she has 19 post-it notes more than him.

Total number of post-it notes that Fiona needs to get from Archie
= 13 + 3
= 16

Answer(s): 16