Solve the following

Given nC12 = nC6

Using nCr = nCn−r 

⇒ n − 6 = 12

 n = 18

$\Rightarrow^{18} C_{2}=\frac{18 \times 17 \times 16 !}{16 ! \times 2}$

$=9 \times 17$

i.e 18C2  = 153