The sum to infinity of geometric series is A/1-r
Where A is the first term in the sequence
And R is the common ratio and R should be less than 1 and greater than -1
so in the sequence of 3+ 9/4 + 27/16 +....
A=3
R=0.75
Use the formula A/1-r
3/1-0/75 = 12
Second sequence 4 + 8/3 + 16/9 +....
A=4
R=2/3
4/1-(2/3) = 12
There they are equal