Since y is just a constand we can just take it out unless your doing derivative with respect to y but in this case its with respect to x.
first you rewrite -(2/x)y=e ^1/x
as -(2x^(-1/2))y = e^1/x
by power rule the derivative is -(x^(-3/2))y= e^1/x (1/2x^-(3/2)
note the derivative of (e^to anything lets say g(x) is just e^to that same number g(x) times the derivative of g(x) for example: e^x^2 the derivative would be e^x^2 times 2x