I ahve theis pice of c code where i have the array equal a value i
want to chaneg those numbers to randon numbers. Part of the code can
be put soemwhere else if need be.
else if(simulation == 2){
     obsticles[0].x = 10;( i need this numebr to eb random)
obsticles[0].y = 40( i need this number to be random);
     obsticles[1].x = 11; obsticles[1].y = 40;
     obsticles[2].x = 12; obsticles[2].y = 40;
     obsticles[3].x = 13; obsticles[3].y = 40;
     obsticles[4].x = 14; obsticles[4].y = 40;
     obsticles[5].x = 15; obsticles[5].y = 40;
     obsticles[6].x = 16; obsticles[6].y = 40;
     obsticles[7].x = 17; obsticles[7].y = 40;
     obsticles[8].x = 18; obsticles[8].y = 40;
     obsticles[9].x = 19; obsticles[9].y = 40;
     x = 14; y = 34;
     targetx = 14;
     targety = 45;
   }

See the example here:
http://www.cplusplus.com/ref/cstdlib/rand.html

As it shows there, you essentially need to:

1) Include the needed files at the top of your file:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

2) If you want different 'random' numbers each time you run your
program, initialize the random number generator based on the system
time like this:

srand ( time(NULL) );

3) get your random number by calling rand() % [the range] + [minimum value].
For example:
 
obsticles[0].x = rand()%100;  // x will be from 0 to 99 inclusive
obsticles[0].x = rand()%10 + 30; // x will be from 30 to 39 inclusive.

Hope this helps.