(19 - x) + 2 3/4 = 5.5

19 - x + 11/4 = 5.5

x + 19 + 11/4 = 5.5

x + 19 = 5.5 - 11/4

x + 19 = 5.5 - 2.75

x + 19 = 2.75

-x = 2.75 - 19

-x = -16.25

x = 16.25

Ответ: x = 16.25