If a problem asks you to find the difference of two numbers, what operation would you perform?

If all of a roofing company`s 6 workers are required to staff 2 roofing crews, how many workers need to be added during the busy season so they can send 4 complete crews out on jobs?

11 members of a bridal party need transported to a wedding reception but there are only 2 4-passenger taxis available to take them. How many will need to find other transportation?