Triple my number add six and subtract twice my number my number plus three

Given situations:

Let my number be X

=> Triple my number = 3x

=> add six = + 6

=> subtract twice my number = - 2x

=> my number plus 3 = x + 3

now, that we simplify each given word phrase, we will now create our equation.

=> 3x + 6 - 2x = x + 3

=> 3x - 2x = x + 3 - 6

=> x = x - 3

=> x - x = - 3

Where x will be cancelled out, thus, this statement is not valid.