300*(10+x)=350*(5+x) 350x+350x5=300x+300x10 350x+1750=300x+3000 350x-300x=3000-1750 50x=1250 50x÷50 =1250÷50 x=25
3000+300x=1750+350x50x=3000-175050x=1250x=1250/50x=25验证300*35=10500350*30=10500