[tex]\it 1000-(126\cdot2+906:6-n):2=807 \Rightarrow (126\cdot2+906:6-n):2 =\\ \\ = 1000-807 \Rightarrow (126\cdot2+906:6-n):2=193|_{\cdot2} \Rightarrow 252+151-n=386 \Rightarrow \\ \\ \Rightarrow 403-n= 386 \Rightarrow n=403-386 \Rightarrow n=17[/tex]