What does the missing number represent?
3 x = 18
(a) the total
(b) the size of the groups
(c) the number of groups
(d) the difference

(C) the number of groups

Step-by-step explanation: It cannot be the total because the total is 18, the size of the groups does not make sense because it seems that you are trying to find a total, and the difference makes no sense because this does not seem like a subtraction problem. (C) the number of groups makes sense because their is a total number of groups.

Hope this helps! :)