When attaching a braille file, it is best to save it as a .brf file, so that it can be opened with various braille programs. However, you have explained the situation well enough that with the attached word file I can give you an answer.
Refer to Rule IX, section 55 of the code book, concerning contractions and short-form words. They may not be used in direct contact with an operation sign (the minus in your example), not can they be used before or after the space which immediately preceded or follows a sign of comparions (the equal sign in your example). The lesson manual, Intro to Braille Mathematics, also shows several examples in section 155. -- Additional Rules for Contractions and Short-Form Words.