#### Answer

Marginal distribution is the sum of counts of each column divided by sample size of 19558
18 to 24 years =$\frac{6432+5640}{19558} = 0.6172 = 61.72%$
24 to 34 years = $\frac{2450+1843}{19558} = 0.2195 = 21.95%$
35 years or older = $\frac{2124+1069}{19558} = 0.1633 = 16.33%$
From this we can deduce that 61.72% of undergraduates are in the age bracket 18 - 24 years

#### Work Step by Step

As given above