Brian bought a 15 pound bag of comcrete. he split the bag into smaller bags that each hold two and a half pounds. how many smaller bags did he fill

6 because 2 and a half + 2 and a half = 5 then 5x3 = 15

Okay. You have 15 lbs of concrete, and x bags that can individually hold 2.5 lbs. What you need to do is divide 15 by 2.5, and the quotient will be 6.

Problem: 15 : 2.5 = 6

So the answer to your problem will be: 6 bags.