Given series is sigma i=1 to infinity 12*
,
=

Clearly it is a geometric series and it converges if and only if r<1
So, common ratio =
< 1
Hence the series is convergent.
Formula for sum of infinite geometric series =

Where a is the first term and r is the common ratio.
So, sum of series =

For taking 2/5 to numerator we have to multiply with reciprocal 5/2 on both numerator and denominator.
Hence sum of series = 12*
= 30