Jimmy is selling used books at a yard sale. a customer buys 9 books at a cost of $0.75 each and pays with a $20.00 bill. jimmy must determine c, the amount of change in dollars he should give the customer. which equation represents c?

20-0.75c=9
20-0.75-9c
0.75(9)+c+20
0.75+9+20

To find your change, first you must determine how much the customer is paying. To find this, you must multiply the cost of one book by the number of books bought.
$0.75 • 9 = $6.75
To find the change, you must subtract $6.75 from $20. $13.25 is your change.
An example of an equation used to solve this would be
0.75(9) + c = $20

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.