Answer:
a) 0.513 = 51.3% probability that a randomly selected voter in the town supports the tax increase.
b) 0.487 = 48.7% probability that a randomly selected voter does not support the tax increase.
c) 0.1777 = 17.77% probability he or she is a registered Independent.
Explanation:
Conditional Probability
We use the conditional probability formula to solve this question. It is

In which
P(B|A) is the probability of event B happening, given that A happened.
is the probability of both A and B happening.
P(A) is the probability of A happening.
Question a:
57% of 46%(democrats)
38% of 42%(republicans)
76% of 12%(independents)
So

0.513 = 51.3% probability that a randomly selected voter in the town supports the tax increase.
Question b:
1 - 0.513 = 0.487
0.487 = 48.7% probability that a randomly selected voter does not support the tax increase.
c. Suppose you find a voter at random who supports the tax increase. What is the probability he or she is a registered Independent?
Event A: Supports the tax increase.
Event B: Is a independent.
0.513 = 51.3% probability that a randomly selected voter in the town supports the tax increase.
This means that

Probability it supports a tax increase and is a independent:
76% of 12%, so:

Thus

0.1777 = 17.77% probability he or she is a registered Independent.