If r is less than q, then it is on the left side because that is the lowest position avaliabe on the number line. If s is q+1, that means s is one more than q so s is bigger than q. If q is more than r and less than s, it is in the middle of those two. So, r is on the left most side, q is in the middle, and s is on the right side because it is the most.
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