Ответ:

а) x = 12 5/12 + 7 1/3 = 12 5/12 + 7 4/12 = 19 3/4.

б) x = 5 7/9 + 2 3/4 − 3 5/12 = 208/36 + 99/36 − 123/36 = 184/36 = 46/9 = 5 1/9.

Ответ: а) x = 19 3/4; б) x = 5 1/9.