17×280＋28×830
＝170x28+28x830
=28x(170+830)
=28x1000
=28000
﹙45×27×64﹚÷﹙15×9×8﹚
＝(45÷15)x(27÷9)x(64÷8)
=3x3x8
=9x8
=72
47×125＋76×47－47
=47×125＋76×47－47x1
＝47x(125+76-1)
=47x(125+75)
=47x200
=9400