1)  

(x - 7) + а = 23,

х = 9,

(9 - 7) + а = 23,

2 + а = 23,

а = 23 - 2,

а = 21,

2)

(11 + х) + 101 = а,

х = 5,

(11 + 5) + 101 = а,

а = 16 + 101,

а = 117