-3[3x-(5x-3)]

I believe your wanting us to simplify this.

-3(3x-(5x-3))

-3((3x-5x-(-3))

-3((3x-5x+(+3))     ---Minus a negative is the same as plus a positive

-3(-2x+3)

6x-9

 

To check that both the simplified version and the original will give you the same answer when the value of x is put it, put a random value for x in both of them. Let's put in 5 for x.

 

Original version:

-3(3x-(5x-3))

-3(3(5)-(5(5)-3))

-3(15-(25-3))

-3(15-22)

-3(-7)

21

 

Simplified version:

6x-9

6(5) - 9

30 - 9

21

 

There we go, it works!