Tonya is buying t-shirts for the members of the band. The company she is buying from charges a flat rate of 15 dollars for shipping and then a set dollar amount per shirt ordered. The table below is a sample of the cost of an order per number of t-shirts ordered.

Number of T-shirts(x): 25 and 30
Cost of order(y): 115 dollars and 135 dollars.

Question

Tonya is buying t-shirts for the members of the band. The company she is buying from charges a flat rate of 15 dollars for shipping and then a set dollar amount per shirt ordered. The table below is a sample of the cost of an order per number of t-shirts ordered. 

Number of T-shirts(x): 25 and 30 
Cost of order(y): 115 dollars and 135 dollars.

anonymous · Answer

1. If Tonya plotted the cost of the orders by allowing "Number of t-shirts" to represent the x-values and the "Cost of Order" to represent the y-values, what are the coordinates of the points that would be on the graph? 
2. Using these coordinates, determine the change in the y-values. 
3. Using these coordinates, determine the change in the x-values. 
4. Determine the slope of the line.