Question 529823
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       7x+8 = 3x+28                        Given

[7x+8]+(-8) = [3x+28]+(-8)                 Adding (-8) to both sides

7x+[8+(-8)] = 3x+[28+(-8)]                 Associative principle of addition

     7x + 0 = 3x+[28+(-8)]                 Inverse principle of assition
   
         7x = 3x+[28+(-8)]                 Identity principle of addition

         7x = 3x+20                        Performing addition

   7x+(-3x) = [3x+20]+(-3x)                Adding (-3x) to both sides.        

   7x+(-3x) = 3x+[20+(-3x)]                Associative principle of addition

   7x+(-3x) = 3x+[(-3x)+20]                Commutative principle of addition

   7x+(-3x) = [3x+(-3x)]+20                Associative principle of addition

   7x+(-3x) = 0 + 20                       Inverse principle of addition
                
   7x+(-3x) = 20                           Identity principle of addition

x[7 + (-3)] = 20                           Distributive principle  

       x(4) = 20                           Performing addition

   [x(4)]·{{{1/4}}} = 20·{{{1/4}}}                         Multiplying both sides by {{{1/4}}}

   x[(4)·{{{1/4}}}] = 20·{{{1/4}}}                         Associative principle of multiplication

       x[1] = 20·{{{1/4}}}                        Inverse principle of multiplication

          x = 20·{{{1/4}}}                        Identity principle of multiplication

          x = 5                           Performing multiplication 

Edwin</pre>