4 gallons milk(m) , 6 bottles water(b), 7 bags chips(c)
4m + 6b + 7c = 27.45
b = 2c
m = b + 1.8....m = 2c + 1.8
4(2c + 1.8) + 6(2c) + 7c = 27.45
8c + 7.2 + 12c + 7c = 27.45
27c + 7.2 = 27.45
27c = 27.45 - 7.2
27c = 20.25
c = 20.25/27
c = 0.75 <== bag of chips
b = 2c
b = 2(0.75)
b = 1.50....bottle of water
m = b + 1.80
m = 1.50 + 1.80
m = 3.30 .....gallon of milk