The correct answer is - 115.
The elevation for the spot marked with the letter X is 115. The reason for that is that the X is on place where the landscape starts to go downwards, thus the elevation is lowering, not increasing like the contour lines prior to it. The contour lines that are in the middle of the picture, where the X and the A markings are, are special contour lines, that have special markings on them, that show us that the landscape is going downwards, not upwards. That can be seen from the little inward lines attached to the contour lines.
Since the highest elevation next to the X is 125 feet, and the X is just bellow the contour line that marks the downfall of the landscape, it will be on approximately 115 feet of elevation.