A triangle has vertices at S(4,1), T(2,-3),and U(4,0). The triangle is translated up 3 units. What are the coordinates of the vertices of the image?

By up I suppose you mean up in y because you have no z coordinate.

Just increase all the y locations by 3 and leave the x coordinates the same.
eg:
S(4,4)

To find the coordinates of the image after translating the triangle up 3 units, we need to add 3 to the y-coordinate of each vertex.

Given the triangle's original vertices:

S(4, 1)
T(2, -3)
U(4, 0)

To translate each vertex up 3 units, we add 3 to the y-coordinate:

For vertex S: (4, 1) -> (4, 1 + 3) -> (4, 4)
For vertex T: (2, -3) -> (2, -3 + 3) -> (2, 0)
For vertex U: (4, 0) -> (4, 0 + 3) -> (4, 3)

Therefore, the coordinates of the vertices of the image after translating the triangle up 3 units are:

S'(4, 4)
T'(2, 0)
U'(4, 3)