One meatball sub sandwich contains 4 meatballs.  Sidney ordered 3 less than ten meatball sub sandwiches. Then Mark ate 4 of Sidney's meatball sub sandwiches. So Sidney ordered another three sub sandwiches.  How many meatballs were in the sub sandwiches that remained?
3 less than ten meatball sub sandwiches is 10-3=<<10-3=7>>7 sub sandwiches.
After Mark ate 4 of Sidney's meatball sub sandwiches, 7-4=<<7-4=3>>3 remained.
Finally, after Sidney ordered three more sub sandwiches, there were a total of 3+3=<<3+3=6>>6 sub sandwiches.
If each sub sandwich has 4 meatballs, then the remaining sub sandwiches contain a total of 6*4=<<6*4=24>>24 meatballs.
#### 24