（1.25+2.5）×16
＝1.25x16+2.5x16
=1.25x8x2+2.5x4x4
=10x2+10x4
=20+40
=60
1.25×3.7×0.8
＝1.25x0.8x3.7
=1x3.7
=3.7
3.4×9+3.4
＝3.4x(9+1)
=3.4x10
=34