（0.3X+0.4X）÷2÷0.3+（0.3X+0.4X）÷2÷0.4=2X+2
等式两边都乘以2*0.3*0.4
(0.3x+0.4)x0.4+(0.3x+0.4x)x0.3=(2x+2)x2x0.3x0.4
0.49x=0.48x+0.48
0.01x=0.48
x=48