This doesn't make sense

The points (a,b) and (c,b) form a segment, and the points (d,e) and (d,f) form a segment. Create an equation assuming the segments are congruent.
Equation: ______

Question 2
Which letters are not used in the equation?

The letters __ and __ are not used.

Question 3
Explain why.
These letters are not used because when the x-values are the same, you subtract the (x-, y-, absolute, or least from the greatest) values to find the length of the segment.

When the y-values are the same, you subtract the (x-, y-, absolute, or least from the greatest)values to find the length of the segment.