①(1/2-5/6+5/12-7/24)×24=12-20+10-7=-5
②2×3.14-8×3.14+5×3.14-9×3.14=3.14(2-8+5-9)=3.14*(-10)=-31.4
③100×(7/10-1/5+1/2-0.01)=70-20+50-1=99
④(1/2-5/6-3/5)×(-30)=-15+25+18=28
①(1/2-5/6+5/12-7/24)×24=12-20+10-7=-5
②2×3.14-8×3.14+5×3.14-9×3.14=3.14(2-8+5-9)=3.14*(-10)=-31.4
③100×(7/10-1/5+1/2-0.01)=70-20+50-1=99
④(1/2-5/6-3/5)×(-30)=-15+25+18=28