Question 411251
let numbers are x and y.

according to question x+y = 31  .......(1)
 and 

 x = y/2 + 4 ...................(2)

now, from (2)   x-4 = y/2 

=> 2x - 8 = y    

from (1)we find y = 31-x  

compare both value of y...

2x-8 = 31-x 

=>  2x + x = 31+8  

=> 3x = 39

=> x = 13 

y = 31-13= 18


so, numbers are 13 and 18 . 

there are many ways to solve this problem, understand the concept and try to solve it yourself.......