The unknown variables are adult tickets or A, and children tickets or C.
So for every adult ticket sold, the number of tickets is times the cost which is 11 dollars. Hence, if you sold 2 adult tickets, what you've made can be calculated as 2 x 11. And so on for any number of tickets. The same method applies for children tickets, that is, variable C, which is 2 dollars each.
Therefore the equation to represent this can be expressed as follows;
Each A ticket is $11 and each C ticket is $2. the sales of both tickets all together is
11 times A + 2 times C
11A + 2C
This is the algebraic expression that can be used to determine how much was made for any number of tickets sold.
For the total money raised by selling 228 adult tickets and 384 kids tickets, the expression can be written as follows;
Profit = [228 * 11] + [384 * 2]
Profit = 2508 + 768
Profit = 3276
The total money raised is $3,276
Note that expressing the total money raised "in algebraic expression" simply means stating your answer while still including the UNKNOWN VARIABLES (A and C). Therefore the total money money raised IN ALGEBRAIC EXPRESSION, is Profit = 11A + 2C
Lets look at the first variable, the adult tickets. Each ticket costs $11. If you were to sell 2 tickets that would be 2 times $11 which is $22. If you were to now sell 10 tickets, That would be 10 times $11, right? And that gives you $110.
If the profit made is calculated as number of tickets sold times the cost of each ticket, then it means the number of ticket being represented by an unknown variable is as good as being given a clear number to work with. So right now, you have not been given a number of tickets as 10, but rather you have been given a number of tickets as letter A. Refer to the question and you would see that its stated, "A = the number of adult tickets..."