If two angles are both vertical and supplementary, then the angles are

a.)obtuse
b.)right
c.)acute
d.)adjacent

Vertical angles are equat.
Supplementary angles add up to 180 degrees.
Let the angles be x and y, then
x = y and x + y = 180
x + x = 180
2x = 180
x = 180/2 = 90

Therefore, the angles are right.