1. **State the problem:** We are given the midpoint M(65.5, 58.5) of segment ST and one endpoint S(66, 19). We need to find the coordinates of the other endpoint T(x, y). 2. **Formula used:** The midpoint formula is $$M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right)$$ where $(x_1, y_1)$ and $(x_2, y_2)$ are the coordinates of points S and T respectively. 3. **Apply the formula:** Given $M = (65.5, 58.5)$ and $S = (66, 19)$, let $T = (x, y)$. Then $$65.5 = \frac{66 + x}{2}$$ $$58.5 = \frac{19 + y}{2}$$ 4. **Solve for $x$:** Multiply both sides by 2: $$2 \times 65.5 = 66 + x$$ $$131 = 66 + x$$ Subtract 66 from both sides: $$131 - 66 = x$$ $$x = 65$$ 5. **Solve for $y$:** Multiply both sides by 2: $$2 \times 58.5 = 19 + y$$ $$117 = 19 + y$$ Subtract 19 from both sides: $$117 - 19 = y$$ $$y = 98$$ 6. **Final answer:** The coordinates of point T are $$T = (65, 98)$$