Step by step
The question
Question: which rule shows that triangles ABC and DEF 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: A with D, B with E, C with F.
DEF is turned over.
That does not matter.
Angle A and angle D are both 40°: a pair of equal angles.
A for angle.
Angle C and angle F are both 60°: a pair of equal angles.
A for angle.
AB and DE are both 7: a pair of equal sides.
S for side.
2 Find the rule
AB is not between the two angles: it does not touch corner C.
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.