15:1.79 or 12:1.49
make fractions
15/1.79
12/1.49
find LCM of 12 and 15
find factors of 12 and 15
12=2 times 2 times 3
15=3 times 5
LCM=2 times 2 times 3 times 5=60
multiply 15/1.79 by 4/4=60/7.16
multiply 12/1.49 by 5/5=60/7.45
7.45>7.16 so therefor 12oz for 1.49 is better