This is a pretty simple thing, and one of the earlier formulas you should
learn while using Excel spreadsheets:

If you data in row 50 that spans from column C to column M then the
range would be C50:M50 and formula would be

=SUM(C50:M50)

You could put this formula in A50, to show the total on the left, or
put it in N50 or M51 to show it on the right.