The independent variable is the variable whose variation does not depend on another external variable. It is the variable on the x-axis which in this case is the growth of the baby.
Note: The diagram you attached to this question does not include the calibration on the x - axis which will give us the independent variable at point
This, nevertheless, is a very simple task. Locate the point A on the graph and trace it downwards to the x - axis, the value written where the line coincides with the x -axis is the value of the independent variable( growth of the baby) at point A.
3 is larger than all of the values on the line, of which the arrow is pointing. The circle is open, so it means that it is not greater than or equal to.