I'm not sure how to do #3 in this PDF:
tinyurl [.][com][slash] yefzpv8
#3 is the one with the two age distributions; one for 1900, one for 2000.
A is approximate the median for each of the distributions. Look on the y-axis; the little tick mark where 0.5 would be is the median point. Half the population is above, half below. Going horizontally from that tick mark, find the point on each distribution, then read the x-axis at that point. For the 1900 distribution, it looks like the median age is about 23, for the 2000 it looks like 35.
b) for the inter-quartile repeat except find the point on y-axis that corresponds to 0.25 and again to 0.75
c) take it from here.