One-third of a number added to itself equals 3 times the difference of the number and seven.

Step-by-step explanation:

Do this step by step.

Let the number = x

1/3 of a number = 1/3 x

Added to itself 1/3x + x

=

3*(x - 7)

So the equation is

1/3x  + x = 3(x - 7)            Remove the brackets. Collect 1/3x and x

4/3 x = 3x - 21                 Multiply both sides by 3.

4x = 3*(3x - 21)                Remove the brackets again

4x = 9x - 63                    Subtract 9x from both sides

-5x = -63                         Divide by -5

x = -63/-5

x = 12.6

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