In 2005, the median income of high school graduates was $26,505, and the median income of workers with a two-year associate's degree was $35,009. over a 45-year period, approximately how much more money is a worker with a two-year associate's degree likely to earn than a worker with only a high school diploma?

We must assume that both medians will stay the same over the course of the 45-year period. 
We can find the difference in incomes on a yearly basis and then just multiply it by 45.
($35009-$26505)*45=$8504*45=$382680
A worker with a two-year associate's degree will earn $382680 more than a worker with high school diploma.