Complex sentence: At the top, teams were asked a mystery question (How many stairs have you climbed?), and they could receive their next clue if they provide the correct answer (53); otherwise, they had to climb the staircase again.
Split into simpler sentences: At the top, teams were asked a mystery question (How many stairs have you climbed?). If the team provide the correct answer (i.e.: 53), they could receive their next clue; if not, they had to climb the staircase again.