so what we know is that there is a number 1?2 that is divisible by 11.
what was 11 multiplied by to get this number? it must start with "1" since 1*1=1 and end with "2" since 1*2=2 and there is 2 at the end of the product .
so let's try: what is 11*12? 132? yes, that sounds good!
so the missing number is 3 and they each paid 12 dollars.