$\text{a)}{10}^9\cdot {10}^{48}={10}^{9+48}={10}^{57}$

$\text{b)}{10}^6\cdot {10}^{54}={10}^{6+54}={10}^{60}$

$\text{c)}1\text{decylion}={10}^{60}={10}^{48}\cdot {10}^{12}={10}^{48}\text{bilionoˊw}$

$\text{d)}1\text{sekstylion}={10}^{36}={10}^{18}\cdot {10}^{18}={10}^{18}\text{trylionoˊw}$