Question

What's 6x+9 find x

Answer 1

you cannot find x...this is not an equation...there is no equal sign

Answer 2

You cannot solve for x here, as this is an expression, not an equation.

You must have 2 sides of which to apply operations on to isolate x to solve for it.
This is usually done by an equals sign or an inequality.

Answer 3

For example if you had 6x + 9 = 0

Then we can solve for x by subtracting 9 on both sides, then dividing both sides by 6.