Who is asking: Student
The sum of all eight numbers is 39. Hence if you arrange the eight numbers into 2 groups of four as you describe then the sum of each of the 2 groups of four is 39/2. This is clearly impossible and hence the arrangement you are seeking is impossible.
The best you can do is to use these numbers as digits, such as 91 + 32 = 78 + 45Cheers
Claude and Penny