23 is the answer
Case 1:
c=10;
b= ++c + ++c;
Then, b=11 + ++c (as ++c means 1st increment and then assignment, so c+1=10+1=11)
Then b= 11 + 12 (same as above)
So, b=23
Case 2:
c=10;
b= ++c++ +c;
Then, ++c means c value(10) at 1st increment then assignment , so 11 (++c) will get added to the value of c after c++ operation
Again c++ means 1st assignment then increment
After increment(i.e., c++), c =12
Now b=11+12 =23