Wonder Task - linear equations with fractions

In class the other day, students were tasked with creating linear equations (y=mx+b) for stories in their life.  They were given the parameter that the rate of change (slope)  be a positive relationship.  Since we are winding down towards Summer and it has been Teacher Appreciation Week, I thought WE (the Math and Numeracy Community) could have a bit of fun with this activity.  

Here is my story, let's see if it fits

On May 1, I had 10 students in my math class.  Every three days, 2 new students join our class because they heard we are doing exciting mathematics!  How many students will I have at the end of the month, if this pattern continues?

y = is the total number of students

x = is the number of days I have held class

m = is the rate of change 2 students every 3 days, 2/3x

b = is the number of students I had in my initial enrollment.

So my equation is y=2/3 x + 10

What do you all think?  Is this a linear relationship (I have my thoughts, but let's hear yours)?  AND try to come up with your own story.