# Video: Evaluating Variables in Given Linear Equations by Direct Substitution

The equation 𝑐 = 5𝑑 can be used to calculate the total number of CDs Jennifer had listened to d days after she started working as a music producer. How many CDs had Jennifer listened to one day after she started her job?

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### Video Transcript

The equation 𝑐 equals five 𝑑 can be used to calculate the total number of CDs Jennifer had listened to 𝑑 days after she started working as a music producer. How many CDs had Jennifer listened to one day after she started her job?

We’re given this equation 𝑐 equals five 𝑑. We know that 𝑐 equals the total number of CDs Jennifer had listened to and that 𝑑 equals the days after she started working. Remember that when we have a variable and a whole number in front of it, what’s happening here is multiplication. Five 𝑑 represents five times 𝑑. To find the total number of CDs listened to, it will be equal to five times the number of days after Jennifer started working.

In this question, we want to know about one day after she started working. That one is the value of 𝑑 in our equation. So, we’ll have five times one. We know that equals five. And that means 𝑐, the total number of CDs that Jennifer had listened to after one day of working, would be equal to five. We can write our finally answer as five CDs.