139. Find two coprime numbers \(a\) and \(b\) that satisfy the equation:

\[
\frac{5a + 7b}{6a + 5b} = \frac{29}{28}
\]
139. After simplifications, we get $\frac{a}{b}=\frac{3}{2}$, but since by condition $(a, b)=1$, then $a=3, b=2$.