Question 70765
{{{m/2 - 3 = 4}}}
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Before considering the fraction you could add 3 to both sides.  This would have the effect
of removing the -3 from the left side, but it would add 3 to the right side.  The result would
be:
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{{{m/2 = 7}}}
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Then just multiply both sides by 2 to end up with {{{m = 14}}}
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another way you could look at it is that the three on the left side is really the fraction
{{{3/1}}}.
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Because it is a fraction you could multiply it by {{{2/2}}} to give it a common denominator
of 2.  If you do that the equation becomes:
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{{{m/2 -6/2 = 4}}}
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Then combine the two left side terms over the common denominator:
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{{{(m-6)/2 = 4}}}
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Multiplying both sides by 2 to eliminate the denominator results in:
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{{{m-6 = 8}}}
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Finally, add 6 to both sides to get {{{m = 14}}} which is the same answer as before.
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Hope this helps expand your understanding.  You already seem to understand the basic idea 
of common denominators and are now just expanding on other details of working these
problems.  Good for you!