The given postulates are:
hl: Two right triangles are congruent if the hypotenuse and one corresponding leg are equal in both triangles.
sss: Two triangles have the corresponding three sides congruent (3 corresponding sides have the same measure)
aas: Two angles and a side not between those angles are congruent.
sas:Two sides and an angle between those sides are congruent.
asa: Two angles and a side between those angles are congruent.
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In the system you have two triangles that share side AC. Then one side is congrent in the triangles.
The line AC bisects angles BAD and BCD, it means taht the angle is equal up and down that line.
Then, the system has two angles and the side between those angles congruent. Triangles are congruent by asa