Answer:
n = 36
Step-by-step explanation:
The opposite sides of a parallelogram are congruent , that is
AB = DC , substitute values
n - 5 =
n + 7 ( multiply through by 3 to clear the fractions )
2n - 15 = n + 21 ( subtract n from both sides )
n - 15 = 21 ( add 15 to both sides )
n = 36