四则运算(要简便运算),化简求值题各20道答:3x+9=27 12x=300-4x 7x+5.3=7.4, 3x÷5=4.8, 1.4×8-2x=6, 410-3x=170, 3(x+0.5)=21, 1.8x=0.972 x÷0.756=90, 1.5x+18=3x 0.5x+8=43, 6x-3x=18 , ,5×3-x÷2=8 , 0.273÷x=0.35, , 9x-40=5, x÷5+9=21, 48-27+5x=31, 10.5+x+21=56, 0.1(x+6)=3.3×0.4 x+2...