(1)X+31%=39.3 (2)X-18%=65.6 (3)8X+42=178 (4)20X-30=150,

问题描述:

(1)X+31%=39.3 (2)X-18%=65.6 (3)8X+42=178 (4)20X-30=150,

(1)X+31%=39.3x+0.31=39.3x=39.3-0.31x=38.99(2)X-18%=65.6x-0.18=65.6x=65.6+0.18x=65.78(3)8X+42=178 8x=178-428x=136x=136÷8x=17(4)20X-30=15020x=150+3020x=180x=180÷20x=9