Answer:
d = 24
Step-by-step explanation:
The external angle (98°) is equal to the sum of the opposite internal angles (2d°, (2d+2)°). This gives you an equation you can solve for d.
98 = 2d + (2d+2)
96 = 4d . . . . . . . . . . . . subtract 2, collect terms
24 = d . . . . . . . . . . . . . divide by 4
