5 × () - 9 = () how to calculate? If the numbers in brackets are equal, how to operate? Please use the most popular language to say the basic principle and its formula, OK?

5 × () - 9 = () how to calculate? If the numbers in brackets are equal, how to operate? Please use the most popular language to say the basic principle and its formula, OK?

5×（）-9=（）
=> 5×（）-（）= 9
=> 4() = 9
=> () = 9÷4= 2.25

5 × () - 9 = () how to calculate? If the numbers in brackets are the same, please explain the basic principle and its formula. Thank you

You can merge first, i.e
4×（）-9=0
So () = 9 / 4

18-7 × () = 3-2 × () how to calculate? If the numbers in brackets are equal, how to operate? Please use the most popular language to say the basic principle and its formula, OK? Is this also to shift the sign and merge the similar items?
Is it 7 × () 2 × () that should be written later? Please explain the reason. Thank you

Replace the bracket with X, and change the original formula to 18-7x = 3-2x. First, move the 3 on the right side of the equal sign to the left, and change the sign 18-7x-3 = - 2. Then, move the - 7x on the left side to the right, and change the sign 18-3 = 7x-2x. The two numbers on the left side of the sign 18-3 = 7x-2x are directly subtracted. The right side merges the similar term 15 = 5x, that is to say, divide both sides of 5x = 15 by 5 to get x = 3

6×（_ -3) = 2 × () if () is the same, how to calculate it? Can you say the basic principle and its formula in the most popular language
Is it possible to do this: 6 × (_ -3）=2×（）
Namely: 6 × () - 18 = 2 × ()
6×（）-2×（）
4×（）=18
18 △ 4 = 4.5, please correct? Can you say the basic principle and its formula in the most popular language?

The answer is 4.5
Let this number be X
6*（X-3）=2X
6X-6*3=2X
6X-18=2X
4X=18
X=4.5