The answer is y+5, unless y can be defined as a number.
y equals x plus 5 is the equation of a straight line in the x-y plane.
y = -2/5
the Y in the sentence X plus Y equals 5 is Y=3 or 2 if the X is 2 or 3
y = 5
y=5-x
19 + y
x = -2
(y-30)/5=x
2+5 = 7
If: y+5 = 11 Then: y = 6
x=5 y=-3
x=1 y=7