Hi here is the solution
SPOILER: NUMBER PUZZLE SOLUTION
For the number puzzle you first have to subtract the numbers and then add them to get the solution.
Example:
9 + 3 = 612
( 9 - 3 = 6)
(9 + 3 = 12)
Complete Solution:
8 + 5 = ???
8 - 5 = 3
8 + 5 = 13
Door Code = 313