Quiz (1 point)
Prove that:
The following properties may be helpful:
    - if m∠ABC = 180, then ∠ABX and ∠XBC are supplementary
 - if ∠ABC and ∠DEF are supplementary, then (m∠ABC) + (m∠DEF) = 180
 if a + b = c, then b = c + (a ⋅ (-1))
- if m∠ABC = 180, then ∠ABX and ∠XBC are supplementary
 - if ∠ABC and ∠DEF are supplementary, then (m∠ABC) + (m∠DEF) = 180
 if a + b = c, then a = c + (b ⋅ (-1))
if the following are true:
- a = c
 - b = c
 
then a = b
Please write your proof in the table below. Each row should contain one claim. The last claim is the statement that you are trying to prove.