Question 444503
You spent a lot of time and effort telling us how hard the problem is and no time nor effort in trying to solve it.
What do you think is the first step? or any step?
What shall we call the missing number?
and what about the second number?

How would we say "10 times the number" in math talk?
What does "their difference is 81" suggest?
Math is just another language.
You learned texting language easily. You just have to learn how to talk in math.