Hey, thanks for the help. This is what I got so far, but I am stuck at the end part?

int cx, cy;
int sx, sy;
int tx, ty;
int distance1, distance2;

void setup(){
  size(200, 200);
  findCoffee();
}

void draw(){
}

void mouseClicked(){
  findCoffee();
}

void findCoffee(){
  // 1. Clear the background.
  background(255); 
  // 2. Draw the grid lines. No boarders!
  for (int i=1; i<10; i++){
    line(0, i*20, width, i*20);
    line(i*20, 0, i*20, height);
  }
  // 3. Generate cx and cy.
  cx = 20 * int( random(1, 10) );
  cy = 20 * int( random(1, 10) );
  // 4. Generate sx and sy
  sx = 10 * int( random(1, 10) );
  sy = 10 * int( random(1, 10) );
  // 5. Generate tx and ty.
  tx = 75 * int( random(1, 10) );
  ty = 84 * int( random(1, 10) );
  // 6. Calculate distance1.
  distance1 = cityBlockDistance(20, 20, 75, 84);
  // 7. Calculate distance2.
  distance2 = cityBlockDistance(10, 10, 75, 84);
  // 8. Set fill color.
  if (distance1 < distance2){
    fill(45, 0, 255);
  }
  else {
    fill(255, 255, 255);
  }
  // 9. Draw a circle.
  ellipse(20, 20, 10, 10);
  // 10. Set fill color again.
  if (distance1 > distance2) {
    fill(45, 0, 255);
  }
  else {
    fill(255, 255, 255);
  // 11. Draw a square.
  rectMode(CENTER);
  rect(55, 45, 10, 10);
  // 12. set the fill color again.
  fill(0, 128, 0);
  // 13. Draw a triangle.
  triangle( tx-5, ty+5, tx, ty-5, tx+5, ty+5);
}

int cityBlockDistance(int ix, int iy, int jx, int jy){
  return (abs( ??? - ??? ) + ??? );
}