Which statement explains why abc is congruent to a a'b'c' ?

The two given triangles ABC and A'B'C' are congruent by SSS or AA axiom of congruence.

Step-by-step explanation:

Rigid Transformation is a transformation which PRESERVES (keeps it SAME) the LENGTH and the ANGLES in an image and pre- image.

Here, as we can ΔABC goes under Rigid Transformation in to the ΔA'B'C'

⇒Sides AB, BC and AC correspond to the sides A'B',B'C' and A'C' respectively.

Also the ∠A, ∠B and∠C correspond to  ∠A', ∠B' and∠C' respectively.

Now, in  ΔABC and ΔA'B'C

AB  = A'B'

BC  =   B' C'

AC  = A'C'

⇒The two given triangles are congruent by SIDE SIDE SIDE property.

Also, ∠A  = ∠A'

∠B  =   ∠B'

⇒The two given triangles are congruent by ANGLE ANGLE property.

Hence the two given triangles ABC and A'B'C' are congruent by SSS or AA axiom of congruence.

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.