Recognizing Arithmetic Sequences

We have been given the following arithmetic sequence, and we need to decide whether $6$ or $\text{-}6$ is the common difference. $25,19,13,7\ldots$ Let's look for a relation between the terms. $25\xrightarrow{{\color{#0000FF}{-6}}}19\xrightarrow{{\color{#0000FF}{-6}}}13\xrightarrow{{\color{#0000FF}{-6}}}7\xrightarrow{{\color{#0000FF}{-6}}}\ldots$ As we can see, each new term is found by subtracting $6$ from the previous term. Therefore, the common difference is $\text{-}6.$