$$109^7=429^a\\\\
log109^7=log429^a\\\\
7log109=a*log429\\\\
a=\frac{7log109}{log429}$$
$${\frac{{\mathtt{7}}{\mathtt{\,\times\,}}{log}_{10}\left({\mathtt{109}}\right)}{{log}_{10}\left({\mathtt{429}}\right)}} = {\mathtt{5.417\: \!746\: \!197\: \!792\: \!286}}$$
.