A single check can be stopped by taking the piece that is delivering the check or by placing a piece between the attacker and the king. When the king is in check from two pieces at the same time, the only way out is to move the king. It simply is not possible to take or to block two pieces at the same time.
In the following example, a black knight is threatening to capture the white queen, but it is white's turn. In fact, it is white to move and deliver checkmate in seven moves! Click here to see the solution.