tentukan jumlah tak terhingga dri deret geametri 12+8+5 1/2

Un=a×r^(n-1)
U1=a=12
U2=ar=8
12×r=8
r=2/3
S(~)=??
S(~)=a/(1-r)
=11-2/3)
=12/(1/3)=12×3=36

12+8+5=25
½+25=½+25/1
1+25=26
2+1 =3
26/3=8⅔