x on Both Sides

In $5x = 2x+9$, the unknown appears on both sides. The plan is to collect all the x-terms on one side. Subtract $2x$ from both sides, in the same way that you would subtract a number.

$$5x-2x = 2x+9-2x$$

$$3x = 9$$

$$x = 3$$

Check: $5\cdot 3 = 15$ and $2\cdot 3+9 = 15$. Both sides have the same value.

You can add or subtract the same x-term on both sides of an equation. When an equation has x on both sides, use this to collect the x-terms on one side. Then isolate x as before.