The expression $8^{(x+7)}is$ part $ofan$ equation involving other exponential expressions with base $e.$

Which $of$ the following $is$ equivalent $to{8}^{(x+7)}$ and $is$ therefore more useful $in$ solving the equation?

$e^{(ln2)(x+7)}$

$e^{(ln8)(x)}+7$

$e^{(ln2)(3x+21)}$