解：9(x+ 3.4)=68.4x+3.4=68.4÷9x+3.4=7.6x=7.6-3.4x=4.2检验左边=9x（4.2+3.4）=9x7.6=68.4=右边
x-4=9.6÷3x-4=3.2x=3.2+4x=7.2
