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A lot of SEO's recommend Distilled's training course as the default. It goes through a lot of topics and is just $40 a month, so a good way to get the basics covered, although they also go into more advanced topics.

+1 on James' response regarding the fact that positions 73 and 90 really don't make much of a difference (few-to-no people will go that far to look for results). There are a few reasons the right page (or any page at all) won't rank for your keyword. Other results have greater page authority (or come from sites with greater domain authorities)–you can ID these in Moz's Open Site Explorer, or with the Mozbar extension for Chrome, by looking at the top results (top 7 or 10) for "mobile column lifts." Other pages provide more/better information that fits users' search intents–while this is largely subjective, take a look at the top seven-to-10 ranking pages for your keyword term and ID the differences in content (compared to yours). Are they longer? Do they link to valuable follow-up information (either on or off the publishing domain)? Is the quality of the writing better than your own? What about any featured imagery or multimedia/video content? Your competitors may have more linking root domains pointing to their whole domain or to their ranking page. You can check this in Moz's Open Site Explorer, as well as AHREFs.

Thank you.  I think the issue is the lifts are identical except for the capacity, so it's difficult other that differentiating in the title, url & headers that one is 18,000 and the other is 12,000.  I'm thinking that combing them on one page might be the best option.