1. 6 and 7 = 42
   2 and 5 = 10
   4 and 8 = 8
   5 and 9 = ?
    
   
2. 7 and 5 = 1
   9 and 12 = 3
   10 and 15 = 5
   12 and 16 = ?
    
   
3. 1st = 1
   3rd = DEF
   10th = *
   6th = ?
    
   

I need to replace the ? with answers. Please help me.
My name is Michael Rodriguez
I am a student.

Thank you for your help. Michael

For 1 and 2 try the greatest common divisor and the least common multiple functions. For 3 you need to look at a telephone.