What reason can be used to complete this proof?
m∠1 = m∠3 because ∠1 ∼= ∠3.
m∠1 + m∠2 = m∠CXB and m∠2 + m∠3 = m∠AXD ________.
m∠1 + m∠2 = m∠AXD because you can substitute m∠1 for m∠3.
m∠CXB = m∠AXD by the transitive property of equality.
So, ∠AXD ∼= ∠CXB.
because that is given information
because you can measure them with a protractor
by the angle addition postulate
because m∠CXB = m∠AXD