The triangle stu shown on the coordinate grid below is reflected once to map onto triangle s't'u': triangle stu drawn on a 4 quadrant coordinate grid with vertices s is at 8, 6. t is at 2, 2. u is at 5, 1. if vertex t' is at (2, −2), what are the coordinates of vertex s'?

Given that triangle STU is reflected once to map onto triangle S'T'U'.
Given that triangle STU has vertices S(8, 6), T(2, 2), U(5, 1).

If vertex T' is at (2, −2), this means that triangle STU is refrected across the x-axis.

A refrection across the x-axis results in an image that has the same x-value as the pre-image but a y-value that has the opposite sign of the y-value of the pre image.

Thus, a point, say (x, y), refrected over the x-axis will result in an image with coordinate (x, -y)

Therefore, given that the coordinate of S is (8, 6), then the coordinates of vertex S'  is (8, -6).