$\frac{r}{p}\ =q$  

 $\frac{r}{q}\ =\ p$  

 $q\ \times\ r\ =\ p\$  

$a=b\times c\times d$

$\frac{a}{b}\ =\ c\ \times\ d$

$d\ =\frac{a}{b\ \times\ c}\$

$c\ \times\ d\ =\frac{b}{a\ }\$

$\frac{a}{b}=\frac{d}{c}$

$a\ =\frac{b}{c}\ \times\ d$

$d\ =c\ \times\frac{a}{b}$

$\frac{d}{a\ \times\ b}=c$

 $a\ =\frac{c}{b\times d}$  

 $b\ =\frac{c}{a\times d}$  

 $c\ =\frac{b\times a}{d}$  

 $\frac{1}{d}=\frac{a}{c\times b}$  

 $q=\frac{p}{r}\times s\times t$  

 $r\times s=q\times\frac{p}{t}$  

 $s=\frac{r\times s\times t}{p}$  

 $t=\frac{1}{q\times r\times s}\times p$  

 $b=\frac{a}{c\times\sqrt{d}}$  

 $c=\frac{b\times d^2}{a}$  

 $d=\sqrt{\frac{a}{b\times c}}$