For #24 I thought it was relatively straightforward by just observing the graph and choosing the value closest to 80 billion, hence I chose option E, but this was an incorrect choice

For #25 What data refers to the population?

24 ( A ) : in 1980 Total National Heath Expenditure is roughly 70 Billion dollars. In 1980 % of national health expenditure of total health expenditure is 35%. Hence 35% of 70 billion ~= 25 billion, hence A.

25 ( C ) : the left bottom graph is dollar per person and right graph is total dollars hence dividing both values will be total population.

∴ 48 billion ÷ 250 = 192 million ( C )