mohon bantuannya but materia ujian nasional

[tex]hari \: ke \: 1 = a \\ hari \: ke \: 2 = ar = 12\\ hari \: ke \: 4 = a {r}^{3} = \: ar \times {r}^{2} = 27 - - - > \: 12 \times {r}^{2} = 27 \\ {r}^{2} = \frac{9}{4} - - - > r = \frac{3}{2} \\substitusi \: nilai \: r \: pada \: hari \: ke \: 2 = a \times \frac{3}{2} = 12 \: \\ maka \: a = 8. \\ jawaban \: (e) = \frac{8}{12} = \frac{2}{3} [/tex]