$B=\frac{{{30.4}^{7}}{{.3}^{29}}-{{5.14}^{5}}{{.2}^{12}}}{{{54.6}^{14}}{{.9}^{7}}-{{12.8}^{5}}{{.7}^{5}}}$

$=\frac{{{5.2.3.2}^{14}}{{.3}^{29}}-{{5.2}^{5}}{{.7}^{5}}{{.2}^{12}}}{{{2.3}^{3}}{{.3}^{14}}{{.2}^{14}}{{.3}^{14}}-{{2}^{2}}{{.3.2}^{15}}{{.7}^{5}}}$

$=\frac{{{5.2}^{15}}{{.3}^{30}}-{{5.7}^{5}}{{.2}^{17}}}{{{2}^{15}}{{.3}^{31}}-{{2}^{17}}{{.3.7}^{5}}}$

$=\frac{{{5.2}^{15}}.\left( {{3}^{30}}-{{7}^{5}}{{.2}^{2}} \right)}{{{2}^{15}}.3.\left( {{3}^{30}}-{{7}^{5}}{{.2}^{2}} \right)}$

$=\frac{5}{3}$