Good day, Tung. Thank you for the question.
Section 58 of the Nemeth Code says:
In work arranged spatially for computation, only the general omission symbol may be used in braille regardless of how the omission is denoted in ink print. In addition, the number of general omission symbols to be used must be the same as the number of omission signs which occur in ink print.
So, in item 1 of your example print, five general omission symbols will be used.
In response to your next question, the blank spatial form gives the student space to use the opposite operation (addition instead of subtraction) to check their answer, so it should be retained in braille. I would transcribe the blank spatial forms using tactile lines for the vertical lines (because using all general omission symbols gives the inaccurate impression that all the blank areas defined by the lines will be filled).
Last but not least, for items 9 and 10 in your example print, the square and the triangle do represent different values, so we need to keep that distinction in braille. Thank goodness these problems have the vertical lines to designate place value, so I would say you can retain these vertical lines and use the Nemeth Code's square and triangle shapes where they appear.
As always, please do let me know if you have follow-up questions.