12*4*25*3
=(4*25)*(12*3)
=100*36
=3600
（5*5 ）*（6*12)
=25*(6*3*4)
=(25*4)*18
=100*18
=1800
(13*8)*(3*125)
=(8*125)*(13*3)
=1000*39
=39000