Turendil wrote:The english sentence was "With great hope the tyrant ordered those ships to be destroyed.
My sentence ran as follows: Cum magna spe Illae navis ab isto tyranno Iubebantur esse delendam.
Hi Turendil...
Your prof may have taken issue with the fact that you took and active sentence and made is passive. Now, I don't know if that was an option to you or not, but even as a passive statement it's a little off, especially the verb:
Magna cum spe - you don't even need the
cum but it isn't incorrect to use it. If you do, the adjective in a
cum +
abl construction regularly moves outside, e.g., magna cum spe, magna cum laude, summa cum laude, etc.
illae naves -
naves, plural, not
navis, singular.
a tyranno - no need for
iste, which would suggest
that very tyrannt, or
that tyrannt which is a real pain in all our tails.
delere iussae sunt - I would use the perfect tense (perfect, passive, 3rd. pers. plural) of
iubeo here and just the plain ol' infinitive of
deleo.
Grand total:
Magna cum spe illae naves a tyranno delere iussae sunt. Beware, however, that the sentence in English is an active one, so unless your prof told you to change it into the passive it is fubared upwards and sideways.

So, for active:
Magna cum spe tyrannus illas naves delere iussit. Nice and neat.
Best,
Chris