7. (10 points) The value of the expression $\frac{1-\frac{2}{7}}{0.25+3 \times \frac{1}{4}}+\frac{2 \times 0.3}{1.3-0.4}$ is
【Analysis】First, according to the method of simplifying complex fractions, find the result of the operation, determine the values of $m$ and $n$, and then proceed to solve further.
【Solution】Solution: $\frac{1-\frac{2}{7}}{0.25+3 \times \frac{1}{4}}+\frac{2 \times 0.3}{1.3-0.4}$
$$
\begin{array}{l}
=\frac{\frac{5}{7}}{0.25+0.75}+\frac{0.6}{0.9} \\
=\frac{5}{7}+\frac{2}{3} \\
=\frac{29}{21} \\
=1 \frac{8}{21}
\end{array}
$$

Answer: The value of $m+n$ is $1 \frac{8}{21}$.
Therefore, the answer is: $1 \frac{8}{21}$.