Question 1209269
**1. Set up the System of Equations**

Since the parabola passes through the points (-3, 8), (2, 5), and (6, 18), we can substitute these points into the equation y = ax² + bx + c to get a system of equations:

* **For point (-3, 8):** 8 = a(-3)² + b(-3) + c 
    => 9a - 3b + c = 8 
* **For point (2, 5):** 5 = a(2)² + b(2) + c 
    => 4a + 2b + c = 5
* **For point (6, 18):** 18 = a(6)² + b(6) + c 
    => 36a + 6b + c = 18

**2. Solve the System of Equations**

You can solve this system of equations using various methods, such as:

* **Substitution:** Solve one equation for one variable and substitute it into the other equations.
* **Elimination:** Eliminate one variable at a time by adding or subtracting multiples of the equations.
* **Matrix methods:** Use matrix operations (e.g., Gaussian elimination) to solve the system.

**Using a calculator or software (like Python with NumPy), you can find the values of a, b, and c:**

* a = 1/2
* b = -1/2
* c = 9

**3. Calculate a + b + c**

* a + b + c = 1/2 - 1/2 + 9 = 9

**Therefore, a + b + c = 9**