Answer:
5 and 8 are supplementary
3=8 (vertically opposite)
so 5 and 3 are supplementary
also 5 and 6 are supplementary (linear pair)
now we've got
5+3=180°
5+6=180°
3=6
Statement: 5 and 3 are supplementary as 3=8
reason: vertically opposite
statement: 5 and 6 are supplementary
reason: linear pair
statement: 3=6
reason: both are supplementary to a same angle
