Spendings of A, B and C are 80%, 85% and 75%. so we can derive that total spending to be 80% of the total.
Total salary is 444, which means total spending (80%) is approx. $ 355.2 and savings is $ 88.8. B's share in it is 6/22 or approx. $ 24 which 15% of his earning. Hence B's salary should be $ 160.
Is this right OA?
I guess that you are taking in this example the assumption that all salaries are almost the same...
Let's imagine salary A = 10$ and salary C = 10$ ... you will have some troubles to find the good solution.
Even if this way is really smart, the assumption could kill you.