A fraction becomes 9/11 if 2 is added to both numerator and the denominator. If 3 is added to both the numerator and the denominator it becomes 5/6. Find the fraction.
Let the numerator and denominator of the fraction be $x$ and $y$ respectively. Then the fraction is $\frac{x}{y}$
If 2 is added to both numerator and the denominator, the fraction becomes $\frac{9}{11}$. Thus, we have
$\frac{x+2}{y+2}=\frac{9}{11}$
$\Rightarrow 11(x+2)=9(y+2)$
$\Rightarrow 11 x+22=9 y+18$
$\Rightarrow 11 x-9 y=18-22$
$\Rightarrow 11 x-9 y+4=0$
If 3 is added to both numerator and the denominator, the fraction becomes $\frac{5}{6}$. Thus, we have
$\frac{x+3}{y+3}=\frac{5}{6}$
$\Rightarrow 6(x+3)=5(y+3)$
$\Rightarrow 6 x+18=5 y+15$
$\Rightarrow 6 x-5 y=15-18$
$\Rightarrow 6 x-5 y+3=0$
So, we have two equations
$11 x-9 y+4=0$
$6 x-5 y+3=0$
Here x and y are unknowns. We have to solve the above equations for x and y.
By using cross-multiplication, we have
$\frac{x}{-9 \times 3-(-5) \times 4}=\frac{-y}{11 \times 3-6 \times 4}=\frac{1}{11 \times(-5)-6 \times(-9)}$
$\Rightarrow \frac{x}{-27+20}=\frac{-y}{33-24}=\frac{1}{-55+54}$
$\Rightarrow \frac{x}{-7}=\frac{-y}{9}=\frac{1}{-1}$
$\Rightarrow \frac{x}{7}=\frac{y}{9}=1$
$\Rightarrow x=7, y=9$
Hence, the fraction is $\frac{7}{9}$.