I. Latin to English:

1. Caesar never knew how many assassins there were.

2. Quintus asks Pompeius if Brutus' forces are still fighting.

3. Quintus asks the soldiers who are fleeing from battle which lieutenants, Brutus having died, are now in command of the legions.
NB qui...fugiunt is simply a relative clause, so the verb is in the indicative mood. The indirect question is qui...praesint.

4. We did not determine how many farmers Octavian had expelled from their lands.

5. I decided yesterday what sort of duties you would carry out (or: were going to carry out) in the treasury.

6. Quintus could not determine whether Argus was traveling to Capua with his parents or had been left behind at home.

7. Quintus said to the farmer, "Do you know to whom my father's lands have been given?"
NB here we have an indirect question (cui...dati sint) embedded within a direct question (scisne...?)

8. No one was responding to Quintus asking when the decemvirs had arrived at Venusia.
Better still: turn the participle into a clause, thus: "No one was responding to Quintus as he was asking..."

9. I do not understand how Vergil persuaded Octavian not to take away his lands.
NB in this sentence we have an indirect command (ne...adimeret) "nested" within the indirect question (quomodo...persuaserit).

10. The old man was urging Quintus not to enter Venusia asking everyone when Argus had left.
NB this time there is an indirect question (quando...discessisset) within the indirect command (ne...omnibus).

II. English to Latin:

1. senex non intellexit cur Quintus domum redire cupivisset.

2. Quintus iam intellegit cur senex fleverit et Romam mox ambulaturus sit.
NB though the English has "was weeping," the sequence of tenses requires the perfect subjuncitve here (indicating that the weeping occurred earlier in time than the understanding).

3. mox decernemus qui veterani agros Quinti culturi sint.
decerno is 3rd conj., hence the "e" designating future tense. This future puts the sentence in the primary sequence, so "are going to till," which indicates an action subsequent in time to "shall...determine," requires the future active participle (culturi, agreeing in gender and number with veterani) and the present subjunctive of sum (sint here, because 3rd plural is needed with the plural subject).

4. fabula senis audita, Quintus tandem didicit cur parentes Argum lupis reliquissent.
"having heard..." must be rendered by ablative absolute in Latin (so those a's are long); treat "abandon" as a verb of giving, so "wolves" is construed as indirect object, hence dative.

5. coloni qui expulsi erant nesciverunt qui (suorum) amicorum agellos miseros adhuc tenerent.
or
coloni expulsi nesciverunt....
If you choose to use a clause for "who had been driven out," it's only a relative clause and thus requires the indicative (in this instance, pluperfect passive). It would be good Latin, though, to reduce that clause to a simple perfect passive participle. In the indirect question, "which" is an interrogative pronoun, which happens to look just like the relative pronoun; but the verb must be in the subjunctive.

6. cum casam veterem a veteranis ebriis habitatam vidisset, Quintus statim scivit cur Venusiam numquam iterum rediturus esset.
or
casa veteri a veteranis ebriis habitata visa....
The "when" clause here is best translated as a cum clause. An ablative absolute would theoretically be possible, but the two ablative participles would be confusing in this instance (see above).