['Launch Microsoft Excel. ... ', 'Type "Principal" into cell A1 on the Excel worksheet. ... ', 'Enter the amount of the mortgage principal in cell B1.', 'Enter the interest rate in cell B2. ... ', 'Enter the number of months in the loan term in cell B3. ... ', 'Enter the following formula in cell A4, beginning with the "equals" sign:', '\\=B2/1200.']