Creating a joint probability table

#1
I need help figuring out how to create this joint probability table


43 million people in the United States go without health insurance. Sample data representative of the national health insurance coverage is:

18 to 34: Yes: 750 No: 170
35 and older: Yes: 950 No: 130


My question isn't so much how to make that table, but whether or not to use the 43 million as the denominator. For example, to find 18 to 34, Yes, would it be 750/43 million? It must be because it's the only information provided. Yet, it doesn't make sense to me since the 43 million is everyone Without insurance. Anyone understand this?
 
#3
Question.

One of the questions for this problem asks:

If the individual does not have health insurance, what is the probability that the individual is in the 18 to 34 age group?


I"m not sure how to solve this one. Anyone know?