Well, it is impossible. You cannot add 2 negative numbers and get a positive answer. If you add 2 negative numbers, you will always get negative answer only.
But, you can get positive number, by finding difference of 2 negative numbers.
consider number pair -2 and -10.
Their difference is
-2-(-10)=-2+10=8 .
Consider pair -3 and -11
-3-(-11)= 8 too.
You can also get 8 from product of two negative number too.
-2 ×-4 = 8.