<PRE><B>Question 97890</B>
 

  1) 6x +12(10-x) = 84

      6x + 120 - 12x = 84

       -6x + 120 = 84

         120 - 84 = 6x

             36 = 6x

                6 = x

check :

    (6*6) +12(10-6)

   = 36 +12*4

   = 36 +48

    = 84


2) -1/5(10d-5) = 9

   -10d/5  +5/5 = 9

     -2d +1 = 9

       -2d = 9- 1 = 8

        d = - (8/2)

         d = -4

check :

    -1/5(-40-5)

    = 40/5 + 5/5 

     = 8 +1

     = 9


3) let the number = n

   so, 3 times the number = 3*n
 = 3n

    5 times the number = 5*n = 5n

    so, 5 times the  number minus 1 = 5n - 1

      s0, half of 5 times the number - 1 = (5n-1)/2

    so, 3n = (5n-1)/2
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