"Will you say what I told you to the teacher?"
Translation:את תאמרי את מה שאמרתי לךְ למורָה?
Hava, your version sounds much better in English and I suspect it ought to be acceptable in Hebrew to say תאמרי למורה את מה שאמרתי לך? י as Torsten_W suggested above. My first attempt אתה תגיד למורה את מה שאמרתי לך? י was rejected. I maintain that it's much clearer to separate the two indirect objects לך and למורה , rather than confusingly putting them together.
if you notice the given answer it says "את תאמרי את..." which sounds like "at tomri et", the first את (pronounced "at") is the feminine singular "you" as almog said, and the second את (pronounced "et") points at the definite direct object, so the hebrew sentence translates to "you will say what i told you to the the teacher?" which also works in english.