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What costs had Mel incurred when his service just began?

The total cost of Mel's cellular phone was $390 after 9 months. What costs had Mel incurred when his service just began?

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Jason S. | My goal is the success of my students. Knowledge-Patience-HonestyMy goal is the success of my students. K...
4.9 4.9 (115 lesson ratings) (115)
I hope I understand the question...
390/9 = 43 3/9.
43 * 9 months = $387
$390 - $387 = $3.
However, the monthly rate could be $20/month for 9 months = $180
390 - 180 = $210
Most likely more information is needed, just as Pam suggested.
Jamie G. | Spanish Tutor with Master's Degree/Basic Tech HelpSpanish Tutor with Master's Degree/Basic...
Does the problem tell you how much the monthly charge was? Look for that. It may be in the instructions or in a previous question. With the information you gave us, it is only possible to determine how much the cell phone service cost over the course of 9 months, just as in the equation that Jason did, but you need to have a second variable in order to determine how much Mel started with. Otherwise, you would just say that Mel started with $0, but that is probably not what the question is looking for.  
If that is the missing information, here is how you work out that problem: 
Let's say that the monthly charge is $30 (I am making up this number.  You can plug in the right number when you get it.)
Then you take 30 and multiply it by 9 months (30 x 9 = 270)
Then take the total amount that Mel paid (here you told us that it is $390) and subtract from that amount the total amount for 9 months worth of service, which we just calculated to be $270. (So, 390-270 = 120).  If we use the 30 for our "x" variable, then Mel started off with $120 in costs when his service just began. 
Pamela E. | Math Tutor for Middle School, High School, and College LevelsMath Tutor for Middle School, High Schoo...
Are you sure you have listed all the information from the problem? Is there any other information, either in words or in a table or graph?  Looks like more information is needed.