\( \dfrac{8}{\square} = \dfrac{3.2}{4} \)
\( \dfrac{8}{10} = \dfrac{3.2}{4} \)
\(\dfrac{8}{x} = \dfrac{3.2}{4} \Rightarrow 8 \times 4 = 3.2 \times x \Rightarrow x = 10\).