buy or download it.
M&E Fundamentals is a good free online M and E course.
Not the ones with peanuts in them.
You can have any number of free variables. If you have m variables and n linear equations then, if m > n, you will have at least (m - n) free variables.
m,mm,mb
The 2013 BMW X6-M has free maintenance for 4 yr./ 50000 mi..
The 2014 BMW X6-M has free maintenance for 4 yr./ 50000 mi..
The 2011 BMW X6-M has free maintenance for 4 yr./ 50000 mi..
The 2012 BMW X5-M has free maintenance for 4 yr./ 50000 mi..
The 2013 BMW X5-M has free maintenance for 4 yr./ 50000 mi..
The 2010 BMW X5-M has free maintenance for 4 yr./ 50000 mi..
The 2012 BMW X6-M has free maintenance for 4 yr./ 50000 mi..
The 2011 BMW X5-M has free maintenance for 4 yr./ 50000 mi..