Answer
The Earth’s acceleration has a magnitude of $7.4\times10^{-23}m/s^2$.
Work Step by Step
The force that Earth exerts on her is her weight, $(45kg)(9.80m/s^2)=441N$. By Newton’s third law, she exerts an equal (and opposite) force on the Earth.
Apply Newton’s second law to the Earth.
$\Sigma F_x=ma_x$
$441N=(6.0\times10^{24} kg)a$
$a=7.4\times10^{-23}m/s^2$
