4.5=x×2.25％×20％

4.5=x×2.25％×20％ 2.5%X+(20-X)*2.25%=0.485 (x-22)+(x-24)+(x-27)+(x-20)=x (x+2005)/ (x+2004)+(x+2007)/(x+2006)=(x+2008)/(x+2007)+(x+20 0.88（X+20%X)=X+84 x+24=4.5X （20-2x)(20-2x)x>400 x=? (X+X*20%)-[(1200-X)-(1200-X)*20%]=40% X+X*20%-(1200-X)-(1200-X)*20%=40% x-30%x=14x+25%x=20 x-3(20-x)=3x-7(9-x) x/2+x/8+x/12+x/20=1