Create a model to compare these two texting plans:

a. Plan A costs $15 a month, including 200 free texts. After 200, they cost $0.15 each.

b. Plan B costs $20 a month, including 250 free texts. After 250, they cost $0.10 each.

Step-by-step explanation:

Let x = number of texts

For plan A

Plan A costs $15 a month, including 200 free texts. After 200, they cost $0.15 each. It means that plan A has a base cost of $15 monthly and charge $0.15 for (total texts - 200 free texts). The model becomes

Cost of plan A = 15 + 0.15 (x - 200)

For plan B

Plan B costs $20 a month, including 250 free texts. After 250, they cost $0.10 each. It means that plan B has a base cost of $20 monthly and charge $0.10 for (total texts - 250 free texts). The model becomes

Cost of plan B = 20 + 0.10 (x - 250)