rich,
you have to solve it like this:-
Let z = x+iy.
|z|=

x
2+y
2.
|z|-z = (

x
2+y
2) - x -iy and this is = 1+2i.
Equating real and imaginary parts:-
we get, y= -2
and (

x
2+y
2)-x = 1.
put y = -2., take x on the other side and square the whole thing.
we get,
x2+4 = x2+2x+1
i.e. x=3/2
so, finally z= 3/2 - 2i
Please, do rate me .