A man whose bowling average is 12.4 takes 5 wickets for 26 runs and thereby decreases his average by 0.4. The number of wickets, taken by him before his last match is: Option 1) 85Option 2) 78Option 3) 72Option 4) 70Option 5) 64

$Bowling \: avg. = 12.4$
$\frac{(No. of runs)}{(no. of wickets)} = 12.4$
$let\: wickets = x ;$
$No.\: of \: runs = 12.4x$
$\frac{(12.4x + 26)}{(x+5)} = (12.4 -0.4)$
$\Rightarrow \frac{(12.4x + 26)}{(x+5)} = 12$
$\Rightarrow 12.4x + 26 = 12x + 60$
$\Rightarrow 0.4x=34$
$\Rightarrow x=85$

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