I think the greatest common factor is 4
Answer:
Equation is
where
denotes number of cups of orange juice needed by Sam.

Step-by-step explanation:
Let
denotes number of cups of orange juice needed by Sam.
Number of cups needed to make punch 
Number of cups with Sam 
Therefore,

Answer:
Union and Intersection
Step-by-step explanation:
We know that the algebra of sets define the properties and laws of the sets.
The basic operations of sets are,
Union, Intersection, Complement of a set and Equality of sets.
Since, the operations addition, subtraction, multiplication and division are the basic arithmetic operations of numbers.
i.e. they are not in the algebra of sets.
So, we get that out of the given options, the operations in algebra of sets are Union and Intersection.