1/5*{-1/4-1/5*[-1/9-1/10*(-1/8-1/6x)]} =2 l *5
-1/4-1/5*[-1/9-1/10*(-1/8-1/6x)] =10 l +1/4
-1/5*[-1/9-1/10*(-1/8-1/6x)] =10+ 1/4
1/5*[1/9+1/10*(1/8+1/6x)] =41/4 l *5
1/9+1/10*(1/8+1/6x) =205/4 l -1/9
1/10*(1/8+1/6x)=205/4 -1/9
1/10*(1/8+1/6x)=1841/36 l *10
1/8+1/6x=18410/36=9205/18 l -1/8
1/6x=9205/18 -1/8
1/6x=36811/72 l *6
x=36811/12