Does anyone know how to get the days 

System of equations:
y = 6x + 104
y = 10x + 60
 
Method : Substitution
Since the both equation is equal to y, you can substitute one equation for the other equation's y:

y = 6x + 104

10x + 60 = 6x + 104
-6x   -60  =-6x  -60

4x = 44
 
 4      4

x = 11

Answer : It would take 11 days.

To find when the two companies would pay the same amount you would want to find which x value makes the two equations equal.

Two ways to find it:

1. Graph both equations and find the intersection: The x value of the coordinate where the lines intersect is the answer.

When you graph both lines, they intersect at (11,170) so after 11 days both companies will pay the same amount.

2. Set both the equations to each other and solve for x:

6x + 104 = 10x + 60
104 - 60 = 10x - 6x
44 = 4x
11 = x

You get the same number from both methods. 11

So after 11 days, pepsi and cola would pay the same.

NOTE: you can use the same two methods to figure out the other questions. (finding what day both companies pay the same amount)