1.
No problem here, but the next two are in an βexercise groupβ with an introduction and a conclusion, along with an optional title. The two problems of the exercise group should be indented some to indicate the grouping.
N.B. An
<exercisegroup> is meant to hold a collection of (short) exercises with common, shared, instructions. Do not use this structure to subdivide an <exercises> division, as you will eventually be disappointed. Instead, use the available, but under development as of 2019-11-02, <subexercises>, which requires a <title>.


