In an election between two candidates A and B, the number of valid votes received by A exceeds those received by B by 15% of the total number of votes polled. If 20% of the votes polled were invalid and a total of 8720 votes were polled, then how many valid votes did B get?  Choose the correct choice from the following.
A) 2837  B) 2839  C) 2834  D) 2822  E) 2823
Let the total number of votes polled in the election be 100k.   Number of valid votes = 100k - 20% (100k) = 80k   Let the number of votes polled in favour of A and B be a and b respectively.   a - b = 15% (100k) =&gt; a = b + 15k   =&gt; a + b = b + 15k + b   Now, 2b + 15k = 80k and hence b = 32.5k   It is given that 100k = 8720   32.5k = 32.5k/100k * 8720 = 2834   The number of valid votes polled in favour of B is 2834.   Answer:283432.5 /100  * 8720= 
<gadget id="calculator">32.5 /100  * 8720</gadget>
<output>2_834</output>
2834   The number of valid votes polled in favour of B is 2834.   Answer:2834
<result>C</result>
In an election between two candidates A and B, the number of valid votes received by A exceeds those received by B by 15% of the total number of votes polled. If 20% of the votes polled were invalid and a total of 8720 votes were polled, then how many valid votes did B get?