Notice that "cast ballots" and "voted in the election" mean the same thing. I.e.:
60.5% of the voting age voters cast ballots
85.7% of registered voters cast ballots
OK, let
a = # of people voting age
r = # of registered voters
v = # of people who voted
So we can rewrite the first two statements:
0.605 a = v
0.857 r = v
Notice this means:
0.857 r = 0.605 a
Now we want to find r/a (portion of voting age people who were registered), so we can rearrange the equation to say:
r/a = 0.605 / 0.857
and put that into your calculator to get your answer. (And multiply by 100 to get a percentage, if you want). I suggest you Percentage calculator through this you get more results about How to calculate percentage .