a)
[tex]p = a \times b \times h | \div bh| [/tex]
[tex]a = \frac{p}{bh} [/tex]
b)
[tex]v = a \times h | \div a| [/tex]
[tex]h = \frac{v}{a} [/tex]
c)
[tex]k = mn(r - p) | \div mn| [/tex]
[tex] \frac{k}{mn} = r - p[/tex]
[tex]r = \frac{k}{mn} + p[/tex]
