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Solve Equations for a Specified Variable

Solve $r=3p-7$ for $p$ .

$r=3p-7\ \rightarrow\ p=$ _______

$r+7=3p-7+7$

$r+7=3p$

$\frac{r+7}{3}=\frac{3p}{3}$

$\frac{r+7}{3}=p$

$p=\frac{r+7}{3}$

Solve $A=\pi r^{2}$ for $r$ .

$A=\pi r^{2} \rightarrow\ r=$ _______

$\frac{A}{\pi}=\frac{\pi r^2}{\pi}$

$\frac{A}{\pi}=r^2$

$\sqrt{\frac{A}{\pi}}=\sqrt{r^2}$

$\sqrt{\frac{A}{\pi}}=r$

$r=\sqrt{\frac{A}{\pi}}$