so.. if we take the numerator to be say "a", then the denominator will be "a+3"
\(\bf \cfrac{a}{a+3}\textit{ if we add }\frac{1}{2}\textit{ we get then }\cfrac{a+7}{a+3+5}
\\\\\\
thus\implies \cfrac{a}{a+3}+\cfrac{1}{2}=\cfrac{a+7}{a+8}\\\\
-----------------------------\\\\
\cfrac{a+3+2a}{2(a+3)}=\cfrac{a+7}{a+8}\implies \cfrac{3a+3}{2a+6}=\cfrac{a+7}{a+8}
\\\\\\
3a^2+24a+3a+24=2a^2+14a+6a+42
\\\\\\
a^2+7a-18=0\implies (a+9)(a-2)=0
\\\\\\
a=
\begin{cases}
2\implies &\frac{2}{5}\\\\
-9\implies &\frac{3}{2}
\end{cases}\)
either of those two fractions will do
