# How do you solve for P in E=P/(4πd^2) ?

$P = 4 \pi E {d}^{2}$
$\text{multiply both sides by } 4 \pi {d}^{2}$
$E \times 4 \pi {d}^{2} = \cancel{4 \pi {d}^{2}} \times \frac{P}{\cancel{4 \pi {d}^{2}}}$
$\text{hence } P = 4 \pi E {d}^{2}$