a)
[tex]v = \frac{a \times b \times h}{3} | \times 3[/tex]
[tex]3v = abh | \div ah[/tex]
[tex]b = \frac{3v}{ah} [/tex]
b)
[tex]v = \frac{abh}{3} | \times 3[/tex]
[tex]3v = abh | \div ab[/tex]
[tex]h = \frac{3v}{ab} [/tex]