a + b =3 5/6
a - b = 1/6

a= 3 5/6 - b
3 5/6 - b - b = 1/6

a = 3 5/6 - b
-2b = 1/6 - 3 5/6

a = 3 5/6 - b
-2b = -3 4/6

a = 3 5/6 - b
b = -22/6 * 1/2

a = 3 5/6 - b
b= -11/6

a= 3 5/6 - 1 5/6
b = -1 5/6

a = 2
b= -1 5/6



 

х+у=3 5/6      х+у=23/6    (1/6+у)+у=23/6        2у=23/6-1/6    у=22/6:2   у=11/6  у=1 5/6

х-у=1/6          х=1/6+у      х=1/6+11/6         х=12/6      х=2

проверка

2+1 5/6=3 5/6

2-1 5/6=6/6-5/6=1/6