Equation of straight lines: GRE Math Practice Question#5

 
In the $xy$-plane line $l$ has a slope of $m$ and a $y$-intercept of $b$, what is the $x$-intercept of the line $l$ in terms of $m$ and $b$?

1. $\quad -\dfrac{b}{m}$
2. $\quad -\dfrac{m}{b}$
3. $\quad \dfrac{1}{bm}$
4. $\quad \dfrac{b}{m}$
5. $\quad \dfrac{m}{b}$