I think you used the wrong subject.
your answer is B though.
Do you remember when you were learning about the "Least Common
Multiple" of two numbers, and you were wondering why you had to learn
it, because you were so sure that you'd never need to use it ? Do you
remember that ?
Well, HERE's where you get to use it. This question is just looking for
the LCM of 6 and 15 . THAT's how many days it will be before you get
homework in both subjects on the same day again.
(It's not 90 days, and it's not 60 days.)
Answer: 77 - 10 = 67, and the additive inverse of 77 - 10 is 77 + 10. 77 + 10 = 87.
Hope this helps! This question was kind of confusing for me, because I didn’t understand why you said to add 77 - 10… is this is the incorrect answer sorry your question was worded weird