Answer:
If he includes himself then:
Split up the cookies into 4 equal parts.
[tex] \frac{15}{4} = 3.75[/tex]
3.75 cookies each if he includes himself.
If he does not include himself:
Split up the cookies into 3 equal parts
[tex]\frac{15}{3} = 5[/tex]
5 cookies each if he shares to his friends without including himself.
