Adventure play sells an mp3 player for $18.00 and charges $3.25 per song. king music sells a player for $23.00 and charges $2.00 per song. for how many songs will the cost be the same?

System of equations. Start by writing the equation for each one.
For Adventure Play, 18 is the y-intercept (b) and the slope is 3.25 (m). 
y = mx + b
y = 3.25x + 18
For King Music, 23 is the y-intercept and the slope is 2.
y = 2x +23
Since they both equal y, you can set them equal to each other and solve.
2x + 23 = 3.25x + 18
Get x on one side and a variable-free quantity on the other.
3.25x - 2x = 23 - 18
Simplify
1.25x = 5
Then divide both sides by 1.25 to get x by itself.
x = 5/1.25
x = 4
For four songs, the cost will be the same.