I guess it involves the concept of rational numbers and lcm.
Yes, this question is pre-algebra or before, not graduate-school "Advanced Math", as originally posted.
And we need to see where you're getting stuck. (In particular, we need to see what you've done, or else we need to know what sorts of lesson instruction you're needing, so that you can learn the material in the first place.
Ali, Ahmed, and Arham buy a business.
a. Given that Ali pays 3/7 of the cost price and Ahmed pays 9/20 of it, what fraction of the cost price does Arham pay?
This involves adding two fractions and then subtracting from the total (the "whole") of 1. What have you done with this? (
LCM & GCF,
fractions)
b. If Ali pays $7000, how much does the business cost?
You have been given that Ali paid 3/7. In other words, if the total cost is divided into 7 parts, he paid three of those parts. That leaves four remaining parts, on top of his $7,000, to get to the total. What would be the value of another three of those parts? (Hint: It's still the same number, so copy this down.)
This leaves you with one of the parts. If $7,000 is three parts' worth, then what is one part's worth? (Hint: Divide by 3.)
Add this in. So what is the total? (Hint: Add the three values to get the total value.)
(Note: This exercise is poorly constructed, in that you will
not get a nice neat whole-number answer.)
If you get stuck, please reply with a clear listing of your thoughts and efforts so far. Thank you!