Afactory needs to produce 1,800 jars of peanut butter on a certain day. they start production at 8: 30 a. m. by 10: 30 a. m., they have produced 600 jars of peanut butter. at what time will they complete the total number of jars that they need to produce

Let's figure the unit rate:

600 jars
= 300 jars/hr
  2 hrs

They have already produced 600 jars, but need to produce 1800 total, or 1200 more than they have now.  At 300 jars/hr, that production will take 4 hours, and the job will be complete at four hours after 10:30 a.m., or, in other words, at 2:30 p.m.