I would assume the question is finding x, so this is how you do it:
The distance of Line DF = 15
E is a point that divides the line to make DE and EF to make:
DF = DE + EF
Substitute the values. And perform algebra.
15 = (x + 2) + (x + 5)
15 = x + x + 2 + 5
15 = 2x + 7
15 - 7 = 2x
8 = 2x
8/2 = x
4 = x
To make sure of the answer, substitute the x value with 4.
15 = (4 + 2) + (4 + 5)
15 = 6 + 9
15 = 15
Glad to help.
