Chapter 9 Quadratic Relations and Conic Sections - 9.1 Apply the Distance and Midpoint Formulas - 9.1 Exercises - Skill Practice - Page 617: 12

$$\left(\frac{29}{2},\:0\right)$$

Using the distance formula, we find: $$\sqrt{\left(18-11\right)^2+\left(12-\left(-12\right)\right)^2}\\ 25$$ Using the midpoint formula, we find: $$\left(\frac{18+11}{2},\:\frac{12-12}{2}\right)\\ \left(\frac{29}{2},\:0\right)$$