7.8x10x3.6+7.8x10x7.4-7.8
=7.8x(36+74-1)
=7.8x(100+10+1)
=7800+78+7.8
=7878+7.8
=7885.8
14．25－3．83－0．17
=14.25-(3.83+0.17)
=14.25-4
=10.25