Answer:
Unit Rate of Change = 1.27%
Step-by-step explanation:
In 2000, t=1 and Total Music sales = 24.8%
In 2007, t=7 and Total Music sales = 32.4%
The Slope 
The Unit Rate of Change is 1.27% and it means that the Total Music Sales Increased by approximately 1.27% every year.
42 inches of wire will cost 168 cents
Look at the pic to see how to set up the proportion.
Number of items an online shopping site sold per second = 420
Number of items it will sell in 30 minutes =
30 minutes = 1800 seconds
Number of items it will sell in 1800 seconds =
= 1800 × 420
= 756,000
∴ This online shopping site will sell 756,000 in 30 minutes .