1) rearrange formula.
[tex]a=lw\\\\l=\frac{a}{w}[/tex]
2) substitute values.
[tex]l=\frac{42x^{3}y^{4}}{6xy}[/tex]
3) solve.
[tex]l=\frac{42x^{3}y^{4}}{6xy}\\\\\frac{42}{6}=7\\\\ \frac{x^{3}}{x}=x^{2}\\\\\frac{y^{4}}{y}=y^{3}[/tex]
l = 7x²y³
4) verify
[tex]a=lw\\\\a=(7x^{2}y^{3})(6xy)\\ \\a=42x^{3}y^{4}[/tex]
