0.45*99=0.45×（100-1）=0.45×100-0.45=45-0.45=44.55314*0.043+3.14*7.2-31.4*0.15=3.14×4.3+3.14×7.2+3.14×1.5=3.14×（4.3+7.2-1.5）=3.14×10=31.4
