Phoneplus charges $1.75 for the first minute and $.20 for each additional minute. pacbell charges $1.45 for the first minute and $.25 each additional minute. how many additional minutes will it take for the cost of the calls be the same?

So if you have a graphing calculator, simply press the y= button and insert 1.75+.20x into y1 and insert 1.45+.25x into y2 and then press either graph or 2nd graph to get the answer to this question or any others like it and then just look for any points on the graph or table where they intersection or have the same y value at one particular x value.
For instance, on this question, the table and graph will show that they intersect at (7, 2.95). While the table will show table with 1,2,3,4,5,6,7,8, etc. going down on one side. To find the answer you just have to find the point on the next two rows (y1 and y2) that are the same.

However, if you do not own a graphing calculator, simply add .20 to 1.75 til you want to stop (or think the two lines would have intersected by now), and add .25 to 1.45 until you decide to stop ( or you think theyve already intersected by now).