Step-by-step explanation:
we are looking for the greatest common factor of the 3 numbers.
e.g. by prime factorization :
18 = 2×3×3
36 = 2×2×3×3
45 = 3×3×5
the largest chain of prime factor multiplication that is contained in all 3 numbers is 3×3.
the GCF is therefore 3×3 = 9.
and that (9) is the largest possible number of bottles in one box.
oh, and Garth (18 bottles) bought therefore 2 boxes.
Rico (36 bottles) bought 4 boxes.
Mai (45 bottles) bought 5 boxes.