Can someone explain 24 and 25 to me? 24 I got 4.62.2=2.4 so I chose A, but the answer is B. 25 I have no idea how they were able to calculate the 35% (answer E) without calculator

There are two steps you need to complete. The first graph tells you that there is roughly 22 million people in that age range. The second tells you that there are ~25% of people that earn less than 10k, ~10% of people that earn 50k+. From the second graph, we know that the difference in % is 15.
Then, we can multiple 15% by the number of people in the age range to get 3.3 million 
The largest % difference can be found by looking at the age groups and using the equation. Age 85+ has the largest % increase, going from roughly 3 million to 4 million. The percent change here is calculated by doing (4  3) / 3 = 33.33%, which is closest to E.
Hope this makes sense