Make x the subject of this formula:

Question

$$y + 2xb = \dfrac{x}{2b} + 9xb$$

workings: https://i.stack.imgur.com/524y3.jpg

I don't think I'm allowed to subtract xb from both sides like i did.

Answer 1

You can't say $C+xbD=E+xbF\implies C+D=E+F.$

You could say $y=x\left(\dfrac1{2b}+9b-2b\right)$ and solve for $x$ that way.

Answer 2

I have to multiply by $2b$, so: $$2yb - 14xb^2 = x$$

From here, I obtain, picking up $x$: $x(14b^2+1)=2yb$. And so: $$x=\frac{2yb}{14b^2+1}$$