# An MP3 player costs $70 and song downloads cost$0.85 each. How do you write an expression that represents the cost of the MP3 player and x number of downloaded songs. Then find the total cost if 20 songs are downloaded?

Jan 13, 2017

The expression is

$70 + 0.85 n$

For $n = 20$ this works out to $87$

The $70 cost of the mp3 player is a fixed expense. We do not need a variable to express it. The amount spent on music downloads depends on the number of songs we buy, so we use a variable to represent this number, and multiply that variable by the cost of each song. Add the two terms, and you have the total cost. Jan 13, 2017 See the solution process below: #### Explanation: The expression for the Total Cost of Ownership for this MP3 player is: $M = p + c x$Where: $M$is the Total Cost of Ownership for the MP3 player. $p$is the cost to buy the MP3 player -$70 in this case
$c$ is the cost of a CD - $0.85 in this case $x$is the number of CDs purchased - 20 for the problem we are asked to solve. Substituting gives: M =$70 + ($0.85 xx 20) M =$70 + $17 M =$87#