For 8 have you tried just writing out a few of the sets to see what sets you are dealing with? For example, (b) says the sets are .

For n= 1, that is . For n= 2, . For n= 3, . Each of those sets is contained in the previous one. So theunionis just the biggest set, the first one. Theintersectionwill be numbers that are inallthem. Of course, goes to 0 as n goes to infinity. The right boundary is always 1.

For 9, is the set of all rational numbers between 0 and x. What happens as x gets larger and larger?