(0.1x-0.2)/0.02+(x+1)/0.5=350(0.1x-0.2)+2(x+1)=35x-10+2x+2=37x=11x=11/7
sin140度cos20度-cos140度cos70度=sin140度cos20度-cos140度cos20度=sin(140度-20度)=sin(120度)=√3/2