①
②
③2.1x+7.9x=0.29
④12∶7=x∶0.3
①4x÷1.2=0.5
②2.7x-0.8x=5.7
③1.3x-4×0.8=3.3
④5x-1.3=0.2
⑤4x+6x=26
⑥24+0.4x=100