The correct option is C 6
List the factors of each number. Find the largest number that appears in both lists.
Factors of 12: 12, 6, 4, 3, 2, 1
Factors of 18: 18, 9, 6, 3, 2, 1
The greatest common factor of 12 and 18 is 6.
That means the greatest possible number of plates is 6, because 12 cookies could be put onto 6 plates with 2 cookies on each.
18 slices of cheese could be put onto 6 plates with 3 slices of cheese on each.
The greatest number of plates Mason can prepare is 6.