### Theory:

Two angles and the included side of a triangle are equal to two corresponding angles and the included side of another triangle, and then the triangles are congruent.
Suppose the two angles of the first triangle are $$a$$ degree and $$b$$ degree and the included side is $$x$$ units which are congruent to the second triangle whose angles should be the same $$a$$ degree and $$b$$ degree with the included side $$x$$ units.
Example:
In here the two angles of the first triangle are $$40°$$ and $$60°$$ units, and the included side is $$8$$ units which are congruent to the second triangle whose angles are the same $$40°$$ and $$60°$$ with the included side $$8$$ units.
Important!
ASA stands for "angle, side, angle" and means that we have two triangles with two angles and one side are equal.