Step by step
The question
Question: which rule shows that triangles KLM and RST are congruent?
1 Match the parts
Congruent means the same shape and the same size.
One fits exactly on top of the other.
The order of the letters shows which corners match: K with R, L with S, M with T.
RST is turned over.
That does not matter.
Angle K and angle R are both 35°: a pair of equal angles.
A for angle.
Angle L and angle S are both 100°: a pair of equal angles.
A for angle.
KM and RT are both 9: a pair of equal sides.
S for side.
2 Find the rule
KM is not between the two angles: it does not touch corner L.
Go round: angle, angle, side: A A S.
Two angles fix the third one too, because all three add up to 180°.
The angles fix the shape.
The side fixes the size.
So A A S shows the triangles are congruent.
Let's look back.
First: match the parts.
Last: find the rule.