Answer:
see below
Step-by-step explanation:
1. Linear Pair Postulate
This one is a little questionable, as some definitions of linear pairs require supplementary angles, whereas others only require the intersection of two lines. Check your book or notes for any given theorems regarding supplementary angles.
2. m<ABC+ m<CBD= 180 degrees
The definition of supplementary angles is that two angles are supplementary if their measures sum to 180 degrees.
3. Substitution Property of Equality
From previous step, the 90 degrees was in place of <CBD.
4. m<ABC=90 degrees
moved 90 degrees from left side to the right.
