Let $m>1$ be an integer. Determine the number of positive integer solutions of the equation $\left\lfloor\frac xm\right\rfloor=\left\lfloor\frac x{m-1}\right\rfloor$.

1. Let \( n = \left\lfloor \frac{x}{m} \right\rfloor = \left\lfloor \frac{x}{m-1} \right\rfloor \). This implies that \( n \) is a nonnegative integer.
2. From the definition of the floor function, we have:
   \[
   mn \leq x < m(n+1) \quad \text{and} \quad (m-1)n \leq x < (m-1)(n+1)
   \]
3. To find the range of \( x \) that satisfies both inequalities, we take the intersection of these intervals:
   \[
   mn \leq x < m(n+1) \quad \text{and} \quad (m-1)n \leq x < (m-1)(n+1)
   \]
4. The intersection of these intervals is:
   \[
   \max(mn, (m-1)n) \leq x < \min(m(n+1), (m-1)(n+1))
   \]
5. Since \( m > m-1 \), we have:
   \[
   \max(mn, (m-1)n) = mn \quad \text{and} \quad \min(m(n+1), (m-1)(n+1)) = (m-1)(n+1)
   \]
6. Therefore, the range of \( x \) is:
   \[
   mn \leq x < (m-1)(n+1)
   \]
7. The number of integer values \( x \) in this range is:
   \[
   (m-1)(n+1) - mn = mn + m - 1 - mn = m - 1
   \]
8. We need to sum this number over all possible values of \( n \) such that the range is valid. The range is valid as long as \( mn < (m-1)(n+1) \), which simplifies to:
   \[
   mn < mn + m - 1 - n \quad \Rightarrow \quad 0 < m - 1 - n \quad \Rightarrow \quad n < m - 1
   \]
9. Therefore, \( n \) ranges from \( 0 \) to \( m-2 \). The number of integer values \( x \) for each \( n \) is \( m - 1 \).
10. Summing over all valid \( n \):
    \[
    \sum_{n=0}^{m-2} (m-1) = (m-1)(m-1) = (m-1)^2
    \]
11. However, we need to correct this by considering the sum of the maximum values:
    \[
    \sum_{n=0}^{m-2} (m-1-n) = \sum_{k=1}^{m-1} k = \frac{(m-1)m}{2}
    \]

The final answer is \(\boxed{\frac{m(m-1)}{2}}\).