=9.6+9.9×(100-1)=9.6+9.9×100-9.9×1=9.6+990-9.9=990-0.3=989.7
9.6+9.9*99原式=9.6+(10-0.1)*99 =9.6+990-9.9 =990-0.3 =989.7
9.6+9.9x(100-1)=9.6+9.9x100-9.9x1=9.6+990-9.9=990-9.3=981.7
9.6+9.9×99=9.9×(1+99)=9.9×100=990