Answer
The girl must be 0.64 meters away from the fulcrum
Work Step by Step
We sum the torques about the fulcrum:
$(+ \circlearrowleft) \sum \tau=0$
$9.8m/s^2*45kg*1.6m-x*25kg*9.8m/s^2-1.6m*35kg*9.8m/s^2=0$
$45kg*1.6m-x*25kg-1.6m*35kg=0$
$\frac{45kg*1.6m-1.6m*35kg}{25kg}=x$
$x\approx.64m$
