Art B. answered • 01/04/15

Tutor

5.0
(402)
Ph.D. Chemical Engineer Making Math, Chemistry & Physics More Fun!

Shaya,

Let's break these down into 2 equations. The cost of each call will be charge to place a call (in $) + the number of minutes times the cost per minute.

For Andy:

Cost = 3 + 3x where x is the number of minutes.

For Devon:

Cost = 5 + 2x where x is the number of minutes

The question is asking when do the cost equal each other. To do this, set the equations equal to each other and solve for x:

3 + 3x = 5 + 2x

Subtract 3 from both sides to get:

3x = 2 + 2x

Subtract 2x from both sides to get:

x = 2

So, the time when the cost are equal is 2 minutes.

Now, all we need to do is solve for the cost. We can use either equation:

Cost = $3 + 3x = 3 + ($3/minute)(2 minutes) = $9

**Cost is $9.**

Hope this helps.