First of all, I'll help you change the title slightly. "Master Jiang processes a batch of parts, making 45 pieces a day, which is completed four days later than planned; If there are five more per day, it can be finished four days in advance. How many parts are there in this batch? " Because the sentence "if there are 55 more every day" is unreasonable. If you are a wage earner, the boss suddenly asks you to add 55 to 45. I guess you can't and can't do it!
Solution: Suppose it is completed within χ days.
45×(χ+4)=(45+5)×(χ-4)
The solution is χ = 76.
By "If you do 45 things every day, you will finish it four days later than planned":
45× (76-4) = 3240 (pieces)
I hope you are satisfied!