The amount of data left on a cell phone plan is 6 gb after 8 days. 1.5 gb of data is used each day each day. how much data is available at the beginning of the cycle?

Since the rate of change is constant this is a linear equation of the form:

y=mx+b where m is the rate of change and b is the y-intercept (the initial value in this case)

We know m=-1.5 so

y=-1.5d+b, and we know the point (8,6) so we can solve for b...

6=-1.5(8)+b

6=-12+b

b=18

So our function is:

y=-1.5x+18

Thus the initial amount of data is 18GB