It seems some part of the text is missing, however, since we are talking about 'crests' I guess we are talking about waves.
In a wave, the distance between two consecutive crests corresponds to the wavelength of the wave. Therefore, the distance measured with the ruler is the wavelength of the wave.
The equation of a circle:

(h,k) - the coordinates of the center
r - the radius

Plug the coordinates of the points into the equation and check:


The answer is
F(-2,6).
Answer:
(2, 4).
Step-by-step explanation:
For y = -x the transform is:
( x, y ) reflects to (-y, - x)
So (-4, -2) reflects to (2, 4)
The correct answer for this very hard equation would happen to be 12 because 18+12 happens to equal 30 and 42-30 just so happens to equal 12