Combustion analysis generally tells us the percentages of C, H and O. Your 2045 text goes into depth how to use combustion analysis to find the empirical formula. You can use the MS to determine the molecular weight. Using the percentages from the combustion analysis and the molecular weight from the mass spec data, the molecular formula can be determined. See the example below. Combustion analysis often should be regarded some skeptism because the results can be affected by minute impurities.
A sample combustion analysis indicates 94.08% C and 5.92 % H. Obviously there is no oxygen (94.08+5.92 = 100). The Mass Spectrometer indicates that the mol. weight is 102.14 g/mole.





The mol. formula is C8H6. Using the equation for units of unsaturation, the sum of the double bonds and rings is 6. (See below for calculations)

Shown below are two possibilities: