The segment addition postulate tells you that
... JK + KL = JL
a) Filling in the given information, you have
... 3n + (5n-7) = 25
... 8n = 32 . . . . . . . . . . . collect terms, add 7
... n = 4 . . . . . . . . . . . . . divide by 8
b) Now, you know that
... JK = 3n = 3·4 = 12
... KL = 5n-7 = 5·4-7 = 13
The segments are: JK = 12; KL = 13.
