1) x + (7 + x ) = 11;

x + 7 + x = 11;

x + x = 11 - 7;

2x = 4;

x = 2;

2) x + (4 + х) + х = 16;

x + 4 + x + x = 16;

x + x + x = 16 - 4 ;

3x = 12;

x = 4.