Microsoft Excel has the ability to do calculations for you, by using formulas.
Download the workbook on GFCLearnFree's MS Excel Intro to Formulas tutorial by right clicking on the Practice Workbook link and choosing Save As
Save the File with the following name: Excel Formulas Your Name in your classes dropbox folder.
Open the downloaded file.
Follow all the steps and complete the Challenge.
When you have finished everything save your work using the Save button.