What is

7x-4=-2x+1+9x-5

I assume you want to find x

remember, you can do anything to an equation as long as you do it to both sides

7x-4=-2x+1+9x-5

group like terms

7x-4=-2x+9x+1-5

add like terms

7x-4=7x-4

add 4 to both sides

7x=7x

divide both sides by 7

x=x

true

x=all real numbers

since it sipmlifies to x=x (it could somiplify to 0=0 as well), it is an identity and all real numbers work for x