Answer
AAS, One Triangle
Work Step by Step
Law of sines: $\dfrac{\sin A}{a}=\dfrac{\sin C}{c}$
From the given measurements and information it can be seen that we have two angles and one side which corresponds to $AAS$ configuration.
Also, $\dfrac{\sin 40}{a}=\dfrac{\sin 75}{20}$
This gives information about the angle $B$ that it can be found when two angle are given.
This means that we have only One Triangle.
Hence: Configuration is: AAS, One Triangle.
