（8.1－5.4）÷3.6+85.7
=2.7÷3.6+85.7
=0.75+85.7
=86.45
3.5-3.5x0.98
=3.5x(1-0.98)
=3.5x0.02
=0.07还有3.5-3.5x0.98写了啊