Answer
Option D is correct.
Number of Conrad's marbles = r + 6
Step-by-step explanation
Conrad has 6 more marbles than Rory.
Rory has r marbles.
We are then told to find how many marbles Conrad has.
Conrad's marbles = 6 + (Rory's marbles)
Rory's marbles = r
Conrad's marbles = 6 + r = r + 6
Hope this Helps!!!