Х-(17,11/19-4)=9,1/2

х - (17 11/19 - 4) = 9 1/2 
x - 13 11/19 = 9 1/2
x = 9 1/2 + 13 11/19
x = (9+13)+(1/2+11/19) = 22 + (19+22/38) = 22 + 41/38 = 22 41/38 = 23 3/38
_________________________________
проверка
23 3/8 - (17 11/19 - 4) = 9 1/2
23 3/38 - 13 11/19 = 9 1/2
(23-13)+(3/38 - 11/19) = 10 + (3-22/38) = 10 - 19/38 = 9 38/38 - 19/38 = 9 19/38 = 9 1/2