Answer:
Using join on both table against column CUST_ID will return customer ID, company and total sales
Explanation:
select
CUSTOMERS.CUST_ID,
CUSTOMERS.COMPANY,
SALES.TOTAL_SALES
from CUSTOMERS JOIN SALES
ON
CUSTOMERS.CUST_ID=SALES.CUST_ID
Above query selects required customer id and company table from customers table and total sales from sales table and apply join against customer id
JOIN in sql returns all the row where for a value in first table there is a matching value in second table.