The problem
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Trying to figure out how you added and subtracted 6 in second step. there aren't factors from21 and 26to have a sum of85, so I see 91 does work out for factors of 21 and 26. Just cant qute see how you added and subtracted 6z
thanks
Answer provided by our tutors
redefining 85z as "91z-6z" is used to set up factoring
My preference is always to begin a solution with "a few steps" and then increase the number of solution steps when the additional information is clarifying, as sometimes additional steps can lead to confusion [that comment is not relevant to your question but it is worth mentioning]... the tab titled 'Options' is used to control the number of solution steps and you must already know about that since your inquiry is used for 'a lot of steps'!
