Solve the following pair of linear equations by the method of substitution: $3x + y + 1 = 0$ and $2x - 3y + 8 = 0$.

Form the pair of linear equations for the following problem and find their solution by the substitution method.
$A$ fraction becomes $\frac{9}{11}$ if $2$ is added to both the numerator and the denominator. If $3$ is added to both the numerator and the denominator,it becomes $\frac{5}{6}$. Find the fraction.

If $I$ add $1$ to each of the two given numbers,then their ratio is $1:2$. If $I$ subtract $5$ from each of the numbers,the ratio is $5:11$. Find the numbers.

Solve the following pair of equations by substitution method:
$7x - 15y = 2$ $...(1)$
$x + 2y = 3$ $...(2)$

$A$ fraction becomes $\frac{4}{5}$ if $1$ is added to both the numerator and the denominator. If $5$ is subtracted from both the numerator and the denominator,it becomes $\frac{1}{2}$. Find the fraction.

Solve the following pair of linear equations by the substitution method.
$s-t=3$
$\frac{s}{3}+\frac{t}{2}=6$