Question

find relationship 7:11::31: ?

Answer 1

7/11 =  31/?   
? = 31 * 11 / 7 = 341/7
 
7 : 11  ::  31 : 341/7

Answer 2

 7  =  31
11      ?

By cross multiplication

7×(?)=31×11

?= 341
     7