Answer :
Final answer:
The proportion of return transactions is calculated by dividing the number of return transactions by the total number of transactions, resulting in 20/70.
Explanation:
The question is asking for the proportion of return transactions out of the total number of transactions. To find this, you add together the number of return transactions (20) and the number of sales transactions (50), which gives a total of 70 transactions. The proportion of return transactions is the number of return transactions divided by the total number of transactions, which is 20/70.
Therefore, the correct answer is a. 20/70.
