-8 - 5n = 64 + 3n
+5n +5n add 5n to both sides, 5n's cancel out on the left.
______________
-8 = 64 + 8n
-64 -64 subtract 64 on both sides, 64's cancel out on the right.
______________
-72 = 8n
___ ___ divide 8 on both sides, 8's cancel out from the right.
8 8
n= -9, final answer
