From the data given, we want to construct a frequency distribution table.
The store gives out cards labelled 1 through 10, and the frequency of each card is shown below;
We now have the relative frequency distribution table (as shown above).
From the details provided in the question,
If the card is an even number, the customer gets a 15% discount for that day.
If the card is an odd number greater than 6, the customer gets a 30% discount.
If the card does not fall into any of the above categories, the customer gets a 20% discount.
(a) Therefore, the relative frequency for a 15% discount would be the addition of the relative frequencies of all even numbered cards. This is shown below;
The relative frequency for 15% discount customers is 0.50
(b) The relative frequency for odd numbers greater than 6 would be the addition of all relative frequencies labeled 7 and 9. This is shown below;