Bhavik bought 3 liters of milk and 5 loaves of bread for a total of $11. a month later, he bought 4 liters of milk and 4 loaves of bread at the same prices, for a total of $10.

how much does a liter of milk cost, and how much does a loaf of bread cost?

M = cost of milk
b = cost of bread

3m + 5b = $11
4m + 4b = $10

7m + 9b = $21

After alot of algebra you get the answer 
m = $.75
b = $1.75

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.