Refer to figure.
For this exercise, we will need the following formula: 
NGM = NAM x (GS/TAS) 

To make it easier, we will solve this exercise in 2 steps:

• FIRST STEP: Calculate the NGM range for: 50 000 kg, OAT = ISA (-55°C) and headwind 25 kt.
• SECOND STEP: Calculate the NGM range for: 49 000 kg, OAT -45°C and headwind 25 kt.

FIRST STEP: 
(1) Enter the table at 50 000 kg and read the corresponding distance: 3261 NM.
(2) Read the TAS at the top right of the table: 426 kt (OAT = ISA, therefore, no temperature correction should be applied)
(3) Ground Speed = TAS - headwind 
Ground Speed = 426 - 25 = 401 kt 
(4) Convert 3261 NAM into NGM:
NGM = 3261 x 401/ 426
NGM = approx. 3070 NGM

SECOND STEP:
(1) Enter the table at 49 000 kg and read the corresponding distance: 3063 NAM. 
(2) Adjust this range to account for the increased fuel burn at higher than ISA temperature (ISA +10°C) using the information from note 2A. Fuel burn therefore increases by 0.6%, which is multiplier 1.006, so range decreases by dividing by 1.006. 
3063 / 1.006 = 3044.7 NAM 
(3) Read the TAS at the top right of the table: 426 kt
- Since the temperature changed from ISA conditions to ISA +10°C (-45°C) => we must to do the TAS adjustment: 
- Read Note 2 at the bottom of the table: °C) Increase TAS by 1 knot per degree C above ISA° 
TAS = 426 kt + 10 kt = 436 kt
(4) Ground Speed = TAS - headwind 
Ground Speed = 436 - 25 = 411 kt 
(5) Convert 3044.7 NAM into NGM:
NGM = 3044.7 x 411/ 436
NGM = approx. 2870 NGM

The difference between first and second step = 3070 NGM - 2870 NGM = 200 NGM