Department X started 550 units during the accounting period, completed and transferred out 500 units and had an ending balance of 200 units. units were in beginning goods in process inventory for the department.

150 units

Explanation:

Data given in the question

Started units during the period = 550 units

Completed and transferred out units = 500 units

Ending balance = 200 units

So, by considering the above information, the beginning units is

As we know that

Beginning units = Completed and transferred out units - started units + ending balance

= 500 units - 550 units + 200 units

= - 50 units + 200 units

= 150 units