Hi, this question is not really testing RTD, but its testing how fractions vary when the same number is added to the numerator and the denominator.

remember 2 rules :

1>If the same integer is added to the num and den of a proper fraction then the value of fraction increases.
eg 1/3, add 1 to both N and D we get 2/4 which is greater than 1/3

2>The converse is true for a positive improper fraction.
eg 4/3(1.33), add 1 to both N and D we get 5/4(1.25) which is less than 4/3.

This question does tell us that values are positive but does not tell us whether the fraction d1/r1 is proper or not. So the statement will not hold if the fraction is improper.

This is a rate problem so start with the basic formula d1 = r1(t1) and d2=r2(t2)

The question asks if t1>t2 - you can reorganize the formula to restate is d1/(r1)>d2/(r2)

1) by itself this is clearly not enough becuase we have no rate information - eliminate AD

2) by itself this is not enough becuase we don't have distance information - eliminate B

Together the statement are still not enough. basically together we have the question:
is (d2 + 30)/(r2 + 30) > d2/(r2) When you have division and addition together with variables it is rarely enough because the relationship will be dependent on values, it is best to try some values:

For instance if d2 = 10 and r2 = 50 the question is is 40/80 > 10/50 which reduces to is 1/2 > 1/5 (yes)

But if d2 is 10 and r2 = 10 then the question is is 40/40 > 10/10 - which asks is 1 > 1 - (no)

Therefore together the information is insufficient.

Answer is E, because you do not know the relationship with d2 and r2. Unless that is given you cannot conclude whether 30+d2/30+r2 > d2/r2