pointers and invoking functions???

I have 2 questions on pointers.  I am not sure how to answer.

1. Question deals with pointing the smallest of 3 integers to one pointer.
Given the integer variables  x ,  y , and  z , write a fragment of code that assigns the smallest of  x ,  y , and  z to another integer variable  min .
 Assume that all the variables have already been declared and that  x ,  y , and  z have been assigned values).

Here was my answer that I know is wrong.
[c]
int minimum (x,y,z)
{
if (x<y)
{
min=x;
}
else
{
min=y;
}
if (min<z)
{
min;
}
else
{
min=z;
}
return min;
}


int maximum (x,y,z)

{
if (x>y)
{
int max;
max=x;
}
else
{
max=y;
}
if (max>z)
{
max;
}
else
{
max=z;
}
return max;
}
[/c]


2. I am having trouble "invoking a function.

Here is my question and I have to be honest I do not know how to answer.

eroIt is a function that takes one argument and returns no value. The argument is a pointer to  int . The function stores the value 0 back into the variable pointed to by the argument.
 x is an  int variable that has been declared. Write a statement that sets the value stored in  x to zero by invoking the function  zeroIt .