Rosalee is inviting 5 friends to a party. Each friend will acquire 4 cookies.
So, let's count from 1-5 and give each friend 4 cookies.
1(4) + 1(4) + 1(4) + 1(4) + 1(4)
4 + 4 + 4 + 4 + 4
8 + 4 + 4 + 4
12 + 4 + 4
16 + 4
20.
Rosalee will require 20 cookies in total.
I hope this helps!