Answer :
All really need to do is pick one number. so, we will go with 6 and 87.
6 times 12 is 72 then you subtract that from $87.
That would be 15
To double check, you can use another one. 9 and 123.
9 times 12 is 108. subtract that from 123 and you get 15.
Your answer is B) $15
Hope I helped :)