100+1/10(X-100)=200+1/10[X-(100+1/10(X-100) - 200]
等式两边乘以10 得1000+X-100=2000+X-(100+1/10(X-100) - 200
化简 得 900=1800-(100+1/10(X-100)
(100+1/10(X-100)=900
等式两边乘以10 得 X-100=8000
X=8100