Answer:
Angle 10 = 8 + 5
This is because Angle 10 is alternate angle to the sum of 6 and 5
And angle 6 = Angle 8 as they are alternate angles
Therefore we can just replace angle 6 for angle 8
This is because Angle 10 is alternate angle to the sum of Angle 6 and 5
This is because Angle 10 is alternate angle to the sum of Angle 8 and 5