Eleven members of the middle school math club each paid the same amount for a guest speaker to talk about problem solving at their math club meeting. they paid their guest speaker $1−a−2−. what is the missing digit a of this 3-digit number?

What this question means is that there is a certain number 1x2 that is divisible by 11.

we can simply see what kind of candidates there are. Let's start with 10*11=110.

now, how much is 11*11? it's 121, so not.

12*11? it's  132, and it fits into the question, and the missing number is 3!

so they each paid 12 dollars and gave 132 dollars to the speaker.