Algebra help?! 5 + (x - 5) = x

It says to use properties and definitions of operations to show that the statement is true. Justify each step.
5 + (x - 5) = x

And also this one. Thanks!
(3d + 7) - d + 5 = 2d + 12

1.) 5 + (x - 5) = x
5 + x - 5 = x
x = x

The statement is true.
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2.) (3d + 7) - d + 5 = 2d + 12
3d + 7 - d + 5 = 2d + 12
2d - 2d = 12 - 7 - 5
0 = 12 - 12
0 = 0

The statement is true.
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5 + (x - 5) = x
5 + x - 5 = x
x = x.

also

(3d + 7) - d + 5 = 2d + 12
3d + 7 - d + 5 = 2d + 12
2d + 12 = 2d + 12.

(3d + 7) - d + 5
=(3d-d)+(7+5 )= 2d + 12

slove by varaibles get x by itself