Tiffanie,
Thank you for your question!
You are quite right that a good place to start is "Guideline 10: Expendable (Consumable) Material" of the BANA Guidelines for the Transcription of Early Educational Materials from Print to Braille.
As you know, 10.1.1.h of those guidelines says,
Omit lines, dashes, circles, boxes, etc., indicating a required answer, before or after questions. (Braille Formats 2016, Section 10.5.1)
Notably, 10.1.1.f says,
Leave enough blank space, or lines, for the insertion of the answer with braille writer or slate and stylus. It takes skill to line up a braille writer to insert an answer. Extra blank space is needed.
I suspect that in the examples you shared, the student will not be expected to write in any answers on page 69 but *will* be expected to write in answers on page 63 (which includes larger text and boxes indicating missing material and also says, "Find the number that makes each equation true.").
Hmmm.
One more place to look for guidance is the Math Examples at the end of the BANA Guidelines for the Transcription of Early Educational Materials from Print to Braille. On print page 52 of those guidelines, the commentary to the UEB Math/Science Math Example 3 says,
The visible space symbol (+) representing a space to be filled in is used in textbooks. (UEB Guidelines for Technical Material, 2014, 3.6) However, for worksheets or homework sheets intended for a specific student it may be beneficial to draw squares to identify the missing number as shown on the following page.