63*73-63*63
＝63x(73-63)
=63x10
=630
125x25x64
=125x25x8x4x2
=(125x8)x(25x4)x2
=1000x100x2
=200000
72x26+36x48
=36x2x26+36x48
=36x(52+48)
=36x100
=3600