What is the difference between the average number of bags available in stores P and R together and the average number of bags available in stores S and T together?

% of bags available in stores P and R together = (20 + 15)% = 35%

=> Number of bags available in stores P and R together = $$\frac{35}{100} \times 600 = 210$$

=> Average = $$\frac{210}{2} = 105$$

% of bags available in stores S and T together = (14 + 26)% = 40%

=> Number of bags available in stores S and T together = $$\frac{40}{100} \times 600 = 240$$

=> Average = $$\frac{240}{2} = 120$$

$$\therefore$$ Required difference = $$120 - 105 = 15$$