Tìm x

-7 . ( 5 - x ) - 2 . ( x - 10 ) = 15
4. ( x - 1 ) - 3 ( x - 2 ) = -5
-3 . ( x - 5 ) + 6 ( x + 2 ) = 9
7 . ( x - 9 ) -5 ( 6 - x ) = -6+11x