#### Answer

We see that the equation is false because there is a negative sign missing.
In order to make the statement true, we add a negative sign to create the following statement:
If $ax + b = 0$, then $x = -\frac{b}{a}$.

#### Work Step by Step

If we want to solve for $x$, then we want to isolate $x$.
We first subtract $b$ from both sides:
$$ax = -b$$
We then divide each side by $a$ to get $x$ by itself:
$$x = -\frac{b}{a}$$
We see that the equation is false because there is a negative sign missing.
In order to make the statement true, we add a negative sign to create the following statement:
If $ax + b = 0$, then $x = -\frac{b}{a}$.