Let $h_0$ be the initial time, expressed in hours.
Then $h_0 = 7 + t$ where $0 < t < 1$.
Let $m_0$ be number of minutes for the minute hand at time $h_0$.
Then $m_0=60t$.
Let $h_1$ be the time of the exchanged positions, expressed in hours.
Let $m_1$ be number of minutes for the minute hand at time $h_1$.
It's given that at time $h_1$, the hour and minute hand positions are the same as
for time $h_0$, except that the hour and minute hands are exchanged.
\begin{align*}
\text{Then }\;\;\frac{h1}{12}&=\frac{m0}{60}\\[6pt]
\implies\; h1&=12\left(\frac{m0}{60}\right)=12\left(\frac{60t}{60}\right)=12t\\[10pt]
\text{and }\;\;\frac{m1}{60}&=\frac{h0}{12}\\[6pt]
\implies m1&=60\left(\frac{h0}{12}\right)=60\left(\frac{7+t}{12}\right)=35 + 5t
\end{align*}
From given information, $7 < h_0 < 8$ and $h_0 < h_1 < h_0 + 1$, hence $7 < h_1 < 9$.
Suppose first that $7 < h1 < 8$. Then
\begin{align*}
&h_1 = 7 + \frac{m_1}{60}\\[6pt]
\implies\; &12t = 7 + \frac{35 + 5t}{60}\\[6pt]
\implies\; &t = {\small{\frac{7}{11}}}\\[6pt]
\implies\; & h_0 = h_1 = {\small{\frac{84}{11}}}
\end{align*}
contrary to $h_0 < h_1$.
Thus, we must have $8 \le h_1 < 9$. Then
\begin{align*}
&h_1 = 8 + \frac{m_1}{60}\\[6pt]
\implies\; &12t = 8 + \frac{35 + 5t}{60}\\[6pt]
\implies\; &t = {\small{\frac{103}{143}}}\\[6pt]
\implies\; & h_0 = 7 + {\small{\frac{103}{143}}} \text{ and }
h_1 = 8 + {\small{\frac{92}{143}}}
\end{align*}
Thus, at time $h_0$, the number of minutes since $7$:$00$ is
$$m_0 = 60t = 60\left(\frac{103}{143}\right) = \frac{6180}{143}$$