Complex sentence: It earned $5.9 million on its first day, below the $13 million opening day of "The Expendables" and $10 million opening day of "The Expendables 2".
Split into simpler sentences: It earned $5.9 million on its first day. It fell well below the $13 million opening day of "The Expendables" and $10 million opening day of "The Expendables 2".