Answer :

[tex]500w = 3 \cdot 700\ /:500\\\\w= \frac{\big{3\cdot700}}{\big{500}} \\\\w= \frac{\big{21}}{\big{5}} \\\\ w= 4\frac{1}{5} [/tex]
[tex]500w = 3 * 700 \\ \\ 500 w = 2100 \\ \\ w = 2100 / 500 = 21/5 \\ \\ w = \frac{21}{5} = 4.2 [/tex]