In a certain code language, ‘Numbers are even’ is coded as ‘5 3 +’, and ‘Odd factors are multiples’ is coded as ‘+ 7 6 @’. What can be the code for ‘even’ in that code language?

5 or 3

Given; In a certain code language, ‘Numbers are even’ is coded as ‘5 3 +’, and ‘Odd factors are multiples’ is coded as ‘+ 7 6 @’. 

So,

NUMBERS  ARE  EVEN  =  5   3   +

ODD  FACTORS  ARE  MULTIPLES  =  +   7   6   @

Thus,

Code for even is either 5 or 3.