I was helping a young lady study for the (general) GRE. She was using some study guide she had bought. The math sections are divided into "Arithmetic", "Algebra", "Geometry", "Data Analysis." The Arithmetic sections is pre-high school stuff: Simplify exponents, calculate percents, and such.
At the end of the arithmetic section, was a problem: When a positive integer $n$ is divided by $3$ the remainder is $2.$ When it is divided by $5$, the remainder is $1$. Find the smallest possible value of $n$.
I couldn't come up with a good way for her to work the problem. At this level, she wouldn't put division in the shape of the Division Algorithm, so it took some explaining just to get to "Well, $n =3k+2$ for some $k$."
With the two facts $n=3k+2$ and $n=5m+1$, the best I could do was have her write down some terms of both progressions and discover that $11$ was common to both.
So my question is: Is there some technique from pre-algebra (why is that a thing?) that students typically learn which would help them with this problem? Or is it typical of the GRE to ask a question where the student would have to reason as we did (that is, just listing a few terms)? Or is the study guide just whacked?