What are the x-coordinates of the solutions to this system of equations? . x2 + y2 = 100. y = x + 2. select one: . a. 2 and 10. b. 10 and -2. c. 6 and -8. d. 6 and 8

To answer, substitute the value of y in the second equation to that of the first. 
                                  x² + (x + 2)² = 100
Simplification leads to,
                                  x² + x² + 4x + 4 = 100
                                    2x² + 4x + 4 = 100
                                     x² + 2x - 48 = 0
The roots of this equation are x = 6 and x = -8. Thus, the answer is letter C.