Solve $4x + 3 = x - 9$.

How we read your problem

A linear equation in x: isolate x using inverse operations.

Step-by-step solution

1. 1

   Start with the equation

   $$4~ x+3 = x-9$$
2. 2

   Subtract 1x from both sides

   $$3x + 3 = -9$$
3. 3

   Subtract 3 from both sides

   $$3x = -12$$
4. 4

   Divide both sides by 3

   $$x = \frac{-12}{3} = -4$$

Formulas used

• Linear equation

  $$ax + b = c \;\Rightarrow\; x = \frac{c - b}{a}$$

Doing the same operation to both sides keeps the equation balanced. Undoing addition, then multiplication, leaves x alone.

Verification

• x = -4: left side = -13, right side = -13 ✓