Atransformation of δstv results in δutv. which transformation maps the pre-image to the image?

answer: it is a reflection across the line tv.

explanation:   since, in a reflection we flip an object across a line without changing its size or shape.

here, results in in which,

st=ut (given)

sv= uv (given)

and, tv=tv (common segment)

therefore, by sss postulate,

thus, there is no change in shape or size of the given triangle stv.

hence,   is reflected to across the line tv.