一、5.4÷1.8+240×1.5

=3+360

=363

二、9000÷72×(1.25×0.7×8)

=9000÷72×7

=125×7

=875

三、61-(1.25+2.5×0.7)

=61-3

=58

四、[(10-0.8)+9.85]-2÷0.125

=19.05-2÷0.125

=19.05-16

=3.05