Let the total number of voters be 178,800.
Step 1: Find the total number of voters who cast their votes.
10% of registered voters did not cast their votes, so 90% cast their votes:
\[
\text{Voters who cast their votes} = 0.90 \times 178,800 = 160,920.
\]
Step 2: Find the number of valid votes.
5% of the votes were declared invalid, so 95% of the votes are valid:
\[
\text{Valid votes} = 0.95 \times 160,920 = 152,874.
\]
Step 3: Define the votes obtained by A, B, and C.
Let the number of votes obtained by B be \( x \). Then:
- A obtained 834 votes more than B, so A's votes are \( x + 834 \).
- A obtained 1254 votes more than C, so C's votes are \( x + 834 - 1254 = x - 420 \).
Thus, the total number of valid votes is:
\[
x + (x + 834) + (x - 420) = 152,874.
\]
Step 4: Solve for \( x \).
Simplifying the equation:
\[
3x + 414 = 152,874,
\]
\[
3x = 152,874 - 414 = 152,460,
\]
\[
x = \frac{152,460}{3} = 50,820.
\]
So, B obtained 50,820 votes.
Step 5: Find the number of votes obtained by A (the winner).
A's votes are \( x + 834 = 50,820 + 834 = 51,654 \).
Thus, the number of votes obtained by the winner (A) is 51,654.