A fires 5 shots to B's 3 but A kills only once in 3 shots while B kills once in 2 shots. When B has missed 27 times, A has killed :

Let the no of shots be x. Then, 

Shots fired by A =(5/8)x

Shots fired by B = (3/8)x 

Killing shots by A = 1/3 of (5/8)x  = (5/24)x

Shots missed by B = 1/2 of (3/8)x = (3/16)x 

(3/16)x = 27  $\Rightarrow$x =144

Birds killed by A = (5/24)x = (5/24)*144 = 30