Point t has coordinates (-1,3). point m is symmetric to point t with respect to the line y=1

T (-1, 3) is vertically 2 units away from the line y = 1.
When finding the ordered pair for the new point, M, it must also be 2 units from the line y = 1, but on the opposite of the line. The x-value will not change only the y-value.
Counting two units BELOW the line we get M(-1, -1)