(25-2.5)x4.1
=(25-2.5)x（4+0.1）
=(25-2.5)x4+(25-2.5)x0.1
=100-10+2.5-0.25
=90+2.25
=92.25
{(25-2.5)x4.1中,将4.1拆为（4+0.1）,再把它们各项乘出来（即用4分别乘25和2.5,再相减,然后加上0.1分别乘25和2.5后的和}
12.5x0.7＋12.5
=12.5x0.7＋1.25-1.25+12.5
=12.5x(0.7+0.1)-1.25+12.5
=10-1.25+12.5
=21.25
(2.82x7＋2.82）x1.25
=2.82x(7+1)x1.25
=2.82x(8x1.25)
=2.82x10
=28.2
(6-5.96)x2.5＋0.83
=0.04x2.5＋0.83
=0.1＋0.83
=0.93