montasen

form-of imperfect plural subjunctive third-person

montarの三人称複数過去未完了接続法

English Meaning

third-person plural imperfect subjunctive of montar

Si ellos montasen sus caballos, la aventura sería inolvidable.

もし彼らが馬に乗れば、その冒険は忘れがたいものになるでしょう。

If they rode their horses, the adventure would be unforgettable.