Solution 1:

SELECT a.cust_name,b.order_num FROM Customers a,Orders b WHERE a.cust_id=b.cust_id ORDER BY a.cust_name;

Solution 2:

SELECT a.cust_name,b.order_num FROM Customers a INNER JOIN Orders b ON a.cust_id=b.cust_id ORDER BY a.cust_name;