Answer:
numbers
Explanation:
OH! I wasn't understanding your problem!
It should be In algebra, letters are used in the place of...
but anyways, Letters should be used in the place of NUMBERS.
If I were to say: 6x= 12, then I would be saying 6 times what number= 12
If I said 6 + x = 12, then that would be six + what # = 12.
Anddd so on and so forth for subtraction and division.