Try the following ACT math practice question that tests your understanding of arithmetic sequences.

The first four terms of an arithmetic sequence are $a, x, b, 2x$. The ratio of $a$ to $b$ is

- $\quad \displaystyle \frac{1}{4}$
- $\quad \displaystyle \frac{1}{3}$
- $\quad \displaystyle \frac{1}{2}$
- $\quad \displaystyle \frac{2}{3}$
- $\quad 2$

**Video Explanation**