I think the answer is B. Beth's age is 18 years, and Sally's age is 42 years.
Step 1)
we know that Beth is the younger age brcause the question states that 6 years ago Sally was 3 times as old as Beth so that elimanates options C and D leaving us with options A or B
Step 2)
Next we would subtract 6 from 18 to get 12 and then subtract 6 from 42 to get 36 because we want to get the ages they were 6 years ago.
Step 3)
Now to because the question states that 6 years ago Sally was 3 times as old as Beth, we are going to multiply 12 by 3 to get 36. so this helps prove the fact that Sally was indeed 3 times as old as Beth
Step 4)
finally add back 6 to 12 and 36 to get the sums 18 and 42, and when you add those two you get the remaining sum of 60, so this proves option B is correct
now when we try to apply these same steps to option A
We get 18 - 6 which is 9 and 45 - 6 which is 39, now next step would be to times 9 by 3 to check if it proves that Sally was 3 times older 6 years ago, but 9 x 3 is equal to 27, which is not equal to 39 so that eliminates option A
I hope this helped in some way I'm not to good at explaining stuff ; v ;
