12乘25+0.8乘2.5（用简便方法计算） 13.75乘0.125减0.125乘1.25减0.125乘2.5 （用简便

12x25+0.8x2.5
=4x25x3+2.5x4x0.2
=300+2
=302
13.75x0.125-0.125x1.25-0.125x2.5
=0.125x(13.75-1.25-2.5)
=0.125x10
=1.25