2.3*47+2.4
=2.3*47+4.7-2.3
=2.3*47+0.1*47-2.3
=(2.3+0.1)*47-2.3
=2.4*47-2.3
所以:
1994/(2.3*47+2.4)*(2.4*47-2.3)
=1994