the angle labeled 10 which is =113 and the angle labeled 11 are co interior angles.
co interior angles add upto 180 therefore to get the value of the angle labeled 11 you subtract 113 from 180 which gives you 67
the angle labeled 11 which is =67 and the angle labeled 8 are alternate angles. Alternate angles are equal therefore the value of the angle labeled 8 which you've been asked to give is 67
