410

.

The first digit is the difference between the 2 numbers. The last digit(s) is the sum of the 2 numbers.

5 + 3 = ...

5-3=2 and 5+3=8, thus 5 + 3 = 28

8 + 6 = ...

8-6=2 and 8+6=14, thus 8 + 6 = 214

7 + 3 = ...

7-3=4 and 7+3=10, thus 7 + 3 = 410