Answer:
[tex]{ \tt{sum = \frac{a(r {}^{n - 1} )}{n - 1} }} \\ 27 = \frac{a(r {}^{2 - 1} )}{2 - 1} \\ { \bf{27 = ar - - - (i)}} \\ \\ 54 = \frac{a( {r}^{3 - 1} )}{3 - 1} \\ { \bf{108 = a {r}^{2} - - - (ii) }} \\ { \tt{(ii) \div (i) : }} \\ r = \frac{108}{27} \\ { \bf{common \: ratio = 4}} \\ { \bf{first \: term = \frac{27}{4} }}[/tex]
