Tính 1000 -(138 +171) + (263 - 491)

1000 -(138 +171) + (263 - 491)
-(x + 81 ) = (2x + 12 ) - (5 + x )
(-x + 821 + 534 ) = 499  + (x - 84) 
x + 53 = (400 - 9x ) -- 447