In the given question condition of wheatstone bridge concept is balanced we can draw the circuit according to the concept

Again we can draw it by following diagram

It this satisfy the relation of wheatstone bidge then unknown resistance is negleted hence no current will be drawn from resistance where and

Again we can draw the circuit

And we can calculate in this figure and are in series combination i.e
similarly and are in series i.e
And now and are in parallel combination hence we can calculate
(Because we calculate by parallel combination fomula )
And further resistance are in series combination hence we calculate by