20.5x =x-2.4
20.5x-x=-2.4
19.5x=-2.4
x=-2.4/19.5=-0.123那2+0.5x=x-2.42+0.5x=x-2.42+2.4=x-0.5x4.4=0.5x即x=4.4/0.5=8.8