Question

A12 =? A8=192 r=2 ar7=192  say with steps

Answer 1

it is a geometric series.

r = 2 

$a_n=n'th\ term=a * r^{n-1}\\\\a_8=8th\ term\ =ar^{8-1}=ar^{7}\\\\a_{12}=12th\ term=a*r^{12-1}=a*r^{11}=a*r^{7}*r^{4}\\\\=a_8*r^4=192*2^4=192*16=3072$