Please help me with this question been stuck on it for like 2 days ain`t going no where help

When k2 is open k1 is closed, I = E/R+XBut when k2 is closed, the current which flows through X will be measured by all eyes. Now, let current through X be I1 and through S be I2. let I1+I2 = I3 I3 = E/ (R + XS/ X+S )According to the formula, I1 = I3 × S / (S+X)and I2 = I ( according to problem)substitute the values. you will get X = RS/ (R-X)