3+1/2+(450-3x)/(x+0.2)=450/x
7/2+(450-3x)/(x+0.2)=450/x
（7/2）x（x+0.2）+(450-3x）x=450(x+0.2)
7/2x^2+7/10x+450x-3x^2=450x+90
1/2x^2+7/10x-90=0
5x^2+7X-900=0
x1=12.73 x2=14.135