# Video: Writing and Evaluating Algebraic Expressions in a Real-World Context Involving Decimals

Using 𝑥 to represent the cost of a notebook and 𝑦 to represent the cost of a folder, write an expression for the cost of 3 notebooks and 2 folders. Then, find the total cost, given that the notebooks are \$1.69 each and the folders are \$0.59 each.

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### Video Transcript

Using 𝑥 to represent the cost of a notebook and 𝑦 to represent the cost of a folder, write an expression for the cost of three notebooks and two folders. Then find the total cost, given that the notebooks are one dollar and 69 cents each and the folders are zero dollars and 59 cents each.

Well, if we’re going to form our expression, we can see that we’ve got 𝑥, which represents the cost of a notebook. And we’re gonna have three notebooks. So we can write three 𝑥. And then we’ve got 𝑦, which gonna represent our folders. And we’ve got two folders, so we’re gonna add this. So therefore, our expression for the cost of three notebooks and two folders is three 𝑥 plus two 𝑦.

Okay, great, so now let’s move on to the second part of the question cause we want to find the total cost given that the notebooks are one dollar and 69 cents each and the folders are zero dollars and 59 cents each. So what we’re gonna do is we’re gonna substitute in some values for our 𝑥 and 𝑦. So we know that our 𝑥 is gonna be one dollar and 69, and our 𝑦 is gonna be zero dollars and 59 cents. So therefore, to calculate the total cost, what we’re gonna do is three multiplied by 1.69 plus two multiplied by 0.59, which is gonna give us 5.07 plus 1.18. Which gonna give a total cost for the three notebooks and two folders of six dollars and 25 cents. Okay, great, so we’ve solved this problem. And we’ve found our expression and our total cost.