Answer 1

foo(8) assigns 5 to b
bar(b++) =
incremented b (=6) + b++(=5++)
we know that 6 + 5++ = 11
hence the function returns 11

Answer 2

return bar(b++) calls "bar(6)" function.

Which returns (a + b) or (5 + 6)..

Answer 3

WTF this((((( OMG