As we know the sum of two adjacent angles isand formed linear pair but if their are three angles and sum is its could be linear pair or not?
A linear pair angles are two adjacent angle whose sum is and form a straight line.But if their are three angles and sum is then it is not necessary that it is a linear pair.
As we know in the triangle there are three angle and sum of angles is .So they can be a supplementary angles not necessary a linear pair as they will not always form straight line.