1.
x will be 20
y will be 15
z will be 20

2.
a. Legal. This would return 11.
b. Not legal.  add_one has one parameter and therefore cannot be called without any arguments.
c. Not legal.  You can never call a function without parenthesis.
d. Legal. This would return 0.
e. Not legal.  Again, add_one has one parameter and cannot be called with two arguments.
f. Legal. This would return 17.1.
g. Not legal.  The problem is that inside the function, you would try and add a string and an int, which doesn't work.