Answer:
you have written it a little werid so my answer would be
31 = 1581 = 31
Step-by-step explanation:
7n - 4 = 317n − 4 = 31 (n=5)
7(5) - 4 = 317(5) - 4 = 31
35 - 4 = 1585 - 4 = 31
