"I don't know how to use honorific language."
敬語の使い方がわかりません。
"Do you know how to make a flight reservation?"
飛行機の予約のし方を知っていますか。
The above two sentences were taken from my homework -- which were graded by my sensei, so these should be the correct translations. My question, however, is why is it that in the first example,「が」is used, and in the second example, 「を」is used? Is it due to the fact that "わかりません" in this case is being used in the form of an ability? (Potential forms use the が particle.)