If you were to solve the following system by substitution what would be the best variable to solve and from what equation? 2x+8y=12 3x-8y=11

All the numbers in the first equation have a common factor of 2. Removing that gives
.. x +4y = 6
making it easy to solve for x
.. x = 6 -4y

My choice would be to solve for x using the first equation.

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On second thought, it might actually be easier to solve either equation for 8y. That term then directly substitutes into the other equation (equivalent to adding the two equations).
.. 8y = 3x -11 . . . . . from the second equation
.. 2x +(3x -11) = 12 . . . substituting into the first equation
.. 5x = 23 . . . . . . . . . . collect terms, add 11 (what you would get by adding the equations in the first place)
.. x = 4.6
.. y = (3*4.6 -11)/8 = 0.35