The length of EF would be 12 feet because, in congruent triangles, the corresponding sides are equal in length.
In incongruent triangles, corresponding sides are equal in length. If triangle ABC is congruent to triangle DEF, and the length of line AC is 12 feet, it implies that the corresponding side EF must also be 12 feet. This congruence property ensures that matching sides in congruent triangles share the same length.
Therefore, the length of line EF is equal to the length of line AC, making EF also 12 feet. The concept of congruent triangles plays a crucial role in geometry, providing a basis for understanding and comparing different geometric figures. In this specific case, the given information about the congruence of triangles ABC and DEF allows us to confidently determine the length of EF based on the known length of AC.