4) $$\frac{0,3d - 1,5}{3\frac{1}{3}} = 0,84 : \frac{7}{15}$$;

Решим уравнение:

$$\frac{0,3d - 1,5}{3\frac{1}{3}} = 0,84 : \frac{7}{15}$$.

$$\frac{0,3d - 1,5}{\frac{10}{3}} = \frac{84}{100} : \frac{7}{15}$$.

$$\frac{0,3d - 1,5}{\frac{10}{3}} = \frac{21}{25} * \frac{15}{7}$$.

$$\frac{0,3d - 1,5}{\frac{10}{3}} = \frac{3}{5} * \frac{3}{1}$$.

$$\frac{0,3d - 1,5}{\frac{10}{3}} = \frac{9}{5}$$.

$$0,3d - 1,5 = \frac{9}{5} * \frac{10}{3}$$.

$$0,3d - 1,5 = \frac{3}{1} * \frac{2}{1}$$.

$$0,3d - 1,5 = 6$$.

$$0,3d = 7,5$$.

$$d = \frac{7,5}{0,3} = \frac{75}{3} = 25$$.

Ответ: $$d = 25$$.