Answer:
25,150 units 
Explanation:
The question is to determine the number of production units that were started during the month. 
Note that the company uses the First In First Out method for Process costing
<u>Description                          Units in Process</u>   <u>completion (%)</u>   Equivalent     
                                                                                                      <u>completed (units)                               </u>
The Equivalent Units             28,000                     100              28,000
Subtract:
Opening Work-in- progress    7,500                       60                 4,500
Closing Work in Progress       5,500                        70                3,850
 Equivalent Units Started and Completed                                  19,650
Step 2: Equivalent Units Started 
= Eqivalent Units started and completed +  Total Ending Units    
= 19,650 + 5,500 =     25,150 units