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 9720 votes were polled, then how many valid votes did B get? Pick
A) 1888	B) 2999	C) 3159	D) 2777	E) 2991

Rationale: "let the total number of votes polled in the election be 100 k . number of valid votes = 100 k - 20 % ( 100 k ) = 80 k let the number of votes polled in favour of a and b be a and b respectively . a - b = 15 % ( 100 k ) = > a = b + 15 k = > a + b = b + 15 k + b now , 2 b + 15 k = 80 k and hence b = 32.5 k it is given that 100 k = 9720 32.5 k = 32.5 k / 100 k * 9720 = 3159 the number of valid votes polled in favour of b is 3159 . answer : c"
Answer: C