(3/5-1/2-7/12)×(60×3/7-60×1/7+60×5/7)=(3/5-1/2-7/12)×【60×(3/7-1/7+5/7)】=(3/5-1/2-7/12)×60=3/5×60-1/2×60-7/12×60=36-30-35=-29