puzzle something out
phrasal verb with puzzle verb [ I + adv/prep, T ] uk/ˈpʌz.əl/ us/ˈpʌz.əl/
苦苦思索弄清楚
to discover or understand something by thinking hard about it
[ + question word ] I still can't puzzle out how I managed to spend so much money last month. 我现在仍想不明白上个月怎么花了那么多钱。