Of course Karl is right.
Another way to achieve the same thing but in non distructive way for future reference is, control + A to select all tracks then use the mouse on the edge left or right edge depending on the way you are trying to edit then drag the clip in the direction you want to remove the audio (slip editing). As you ave selected all tracks this will slip edit all tracks at the same time. To undo, select all tracks again and drag in the opposite direction.
Just an alternative to the great advice from Karl.