解:不等式两边同时乘6 5(1.8-8x)-3(1.3-3x)﹥20(5x-0.4) 9-40x-3.9+9x﹥100x-8 -40x+9x-100x﹥-8-9+3.9 -131x﹥-13.1 x﹤0.1