This is what is being asked

1. Calculate the Gs flow rate and the compositions at the top (2) and at the bottom (1) of the tower in molar ratio.
2. Indicate in the molar ratio plot those compositions (note that (2) is a point while (1) is a line)
3. Connect point (2) in the molar ratio plot to the intercept between line (1) and the equilibrium line
4. Find the slope of this new line. This is your minimum Ls/Gs ratio
5. Increase that ratio by 1.5 and draw the new line starting from point (2) and finishing in line (1)

We are designing an acetone-recovery absorption tower. The designed tower needs to recover at least 80% of the acetone present in a gaseous stream of 10 mol% acetone and 90 mol% air. The gas stream flowrate is 150 kmol/h. Assuming that the absorption process happens at 20 C and 101 kPa, the p-x equilibrium data is as follows:

Partial Pressure of Acetone in air (torr)	30.0	62.8	85.4	103.0
Mol % of acetone in water	3.3	7.2	11.7	17.1