Explanation:
We are expected to solve for the range of cost that Sandra will pay to Tonya
firstly, the model for Tonya's charge is
y=3.5+0.5x
For 15 miles
y=3.5+0.5(15)
y=3.5+7.5
y= $11
For 20 miles
y=3.5+0.5(20)
y=3.5+10
y= $13.5
Hence the domain is y=3.5+0.5x 11<=y<=13.5