1cm on map = 2,000,000 cm on the Earth.
2,000,000 cm / 100,000 = 20km
20km / 1.852 (km in a nm) = 10.799nm.
Therefore 1 cm on map = 10.799nm on the Earth.
10.799 x 12 = 129.588nm.
12cm on the map represents 129.57nm on the Earth.