Ponco charges phone users $1.25 for the first minute and $0.30 for each additional minute. cowbell charges users $1.40 for the first minute and $0.25 for each additonal minute. how many additional minutes will it take for the cost of the calls to be the same?

We are going to denote the number of additional minutes with , and the total cost of the call with . 

From PONCO, we know that they charge $1.25 for the first minute, and $0.30 for each additional minute; knowing that our additional minute is  and our total cost of the call is , we can set up an equation to relate the values:
we are going to call this equation (1)

From CowBell, we know that they charge 1.40 for the first minute, and $0.25 for each additional minute. so just like before we can set up an equation to relate the values:
We are going to call this equation (2)

Since the total cost  of equations (1) and (2) is the same, we can equate them to find :





We can conclude that after 3 additional minutes the cost of the calls will be the same; therefore, the correct answer is B.

Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.