yòng / xǐ fà fěn / xǐ tóu / shí / yào / xiān / bǎ / tā / róng jiě / zài / shuǐ lǐ

用洗发粉洗头时，要先把它溶解在水里。

When washing your hair with shampoo powder, you need to dissolve it in water first.