I think this is shown in the fine print on the second sheet . . .
The question starts out by saying that the scale uses two 3V cells in series.
That makes the total battery voltage 6 volts.
0.12 milliamperes = 0.00012 Amperes.
Resistance = (voltage) / (current in Amperes).
Resistance = 6 / 0.00012 = 50,000 Ω