Chart two columns of data in Excel

I'll assume you're using a more recent version of Excel. To make a line graph of your data in the way you described, copy the data columns for MPH and RPM side-by-side in that order. Then select both columns. Click 'Insert' > 'line graph'. To add a trend line and formula for your data, right click on the newly made graph and click 'add trendline' in the dropdown menu. A panel should pop up on the right hand side of your screen with options for the different types of fittings (linear, exponential, logarithmic, etc.).

Hope that helps!