NINA'S POTATO SALAD

INGREDIENTS:
4,6 potatoes, boiled,peeled, sliced,
2 cups diced cooked ham,
1 small onion, finely chopped,
4,5 green lettuce leaves,
1 cup sliced olives,
salt,
pepper.
1/3 cup olive oil,
1/4 cup white vinegar,
2 medium tomatoes, sliced;