Please help me understand this, after solving it, please explain it in detail. Your help is very much appreciated.

8. A corporation owns several companies. The planner for the corporation believes the amount spent on advertising can predict the total sales of the company. She gathers the following sales and advertising information from several of the companies for 2015 (in millions). ADVERTISING 12.5 3.5 21.4 10.5 12.2 8.9 7.6 12.4 18.7 SALES 148 26 120 100 157 58 67 123 196 Develop the equation of the simple regression line to predict sales from advertising expenditures using these data