need help

Ded me now

The common ratio, r,   is 3

The first term = 3

So....this sum is equal to

3 [ 1 - r^*8] / [ 1 - r]  =

3 [ 1 - 3^8] / 1 - 3 ]  

3  [ -6560] / [-2]  =

3 * 3280  =

9840