Which of the following equations has exactly one real solution?

a.2x + 11 = 2x - 18

b.2x + 11 = 2x + 11

c.2x + 11 = -2x - 18

d.2(x + 11) = 2x + 22

The answer is C. 

To solve, add 2x to both sides. Then subtract 11 from both sides. Finally, divide both sides by 4 to get x = -7.5. This is the only equation that has exactly one solution. For answer choices B and D, there are an infinite number of x values so, these two can easily be ruled out. And for answer choice A, there is no solution because the x values cancel each other out.

2x + 11 = -2x - 18
4x + 11 = - 18
4x = -29
x = -7.5

Hope this helps! :)