\(\dfrac{a}{b}=\dfrac{3}{4}\Rightarrow a=\dfrac{3b}{4}\)
Mà \(\dfrac{a-6}{b}=\dfrac{5}{8}\)
\(\Rightarrow\dfrac{\dfrac{3b}{4}-6}{b}=\dfrac{5}{8}\)\(\Rightarrow\dfrac{3}{4}b-6=\dfrac{5}{8}b\Rightarrow\dfrac{1}{8}b=6\Rightarrow b=48\)
\(\Rightarrow a=\dfrac{3b}{4}=\dfrac{3.48}{4}=36\)
Vậy phân số đó là \(\dfrac{36}{48}\)