解:5/8*X+(84-X)*3/4=5/8*X+84*(3/4)-X*3/4=-X/8+63=58即x/8=5所以x=40
两边同时乘以8 得5X+6(84-X)=464 X=6*84-464=40
5/8*X+(84-X)*3/4=5863-3/4x+5/8x=581/8x=5x=40
5/8x+63-3/4x=58 63=58+1/8x x=40