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

% of bags available in stores P and Q together = (18 + 24)% = 42%

Average = $$\frac{42}{2} = 21 \%$$

=> Average number of bags available in stores P and Q together

= $$\frac{21}{100} \times 800 = 168$$

% of bags available in stores R and S together = (30 + 16)% = 46%

Average = $$\frac{46}{2} = 23 \%$$

=> Average number of bags available in stores R and S together

= $$\frac{23}{100} \times 800 = 184$$

$$\therefore$$ Required difference = 184 - 168 = 16