Give an example of a real-world cost that depends on an unknown amount of something. Try to create an expression to represent the total cost.

The equation that can be used to represent the information is the cost of a book is $3, find the number of books when a customer pays $21.

To represent the scenario, the cost of a book is $3, find the number of books when a customer pays $21.

Therefore, the number of books will be:

3x = 21

x = 21/3

x = 7

In conclusion, the correct option is $7.

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Ok, let's suppose that the unknown amount is the number of books you buy in a library. (let's represent this unknown quantity with the variable X)

We know that each book costs $9.75, and we know that in total cost for the X books is $68.25

Then, how many books do you get?

We know that if one book costs  $9.75, then X books will cost X times $9.75

Then the total cost is:

C(X) = X* $9.75

And we know that the total cost was $68.25

Then to solve this, we need to solve the equation:

X* $9.75 = $68.25

X = $68.25/$9.75 = 7

y= -

the mean and mad

step-by-step explanation: