How to work out this word problem?

Question

Dimitrius returned 5 library books last week, returned 3 books this week and then checked out 8 more books. He now has 12 library books. How many books did he have before last week?

Answer 1

You need to change the English sentence into a math sentence (equation).

 

Dimitrius returned 5 library books last week,   returned 5 => -5

returned 3 books this week   Returned 3 => -3

and then checked out 8 more books.  checked out 8 => +8

He now has 12 library books.  Now has 12  => 12

How many books did he have before last week?  the unknown call it B for books

 

B -5 -3 +8 = 12

 

can you solve that?