Question 985367
I will assume answer B left off a 21

First step, see which potential solutions meet the income ratio.
Which incomes are in a ratio of 4:3??
A B and C meet that requirement.

Given three options, you are told both gentlemen save 6000 after their expenses. 
For option A, in order to save 6000 on an income of 18000, Paul would have expenses of 12000. You are told the ratio of expenses is 3:2. That says Peter must have 18000R expenses. Subtract Peter's expenses from his 24000R income. Is that equal to 6000? Yes. So A is an answer.

Now use that same logic on options B and C to see if they, too, are solutions. 

You can do this!