A. If a rice costs $1.33 per kilogram, then 1.3 kg will cost 1.33 * 1.3 = 1.729. We can round it $1.73.
B. If a milk costs $0.71 per liter, with $3.00 you can buy 3 / 0.71 = 4.22 liters (after rounding to the hundredth).
C. In (A) we have cost of standard amount and an information how many of rice we want to buy. We find it by multiplying. In (B) we have cost of standard amount and an information about how much money do we have. We find it by dividing.