It is a linear because it’s a constant rate of change
Answer:

Step-by-step explanation:
The total cost would be "Y".
"x" is would be "per text message".
12 cents per text message would be .12x.
And then, on top of that, we have to pay $30 per month. ( + 30 )
Put together, the equation should be y = .12x + 30.
Go choose the one you think