Form the pair of linear equations in the following problems,and find their solutions (if they exist) by the elimination method.
The sum of the digits of a two-digit number is $9$. Also,nine times this number is twice the number obtained by reversing the order of the digits. Find the number.

On comparing the ratios $\frac{a_{1}}{a_{2}}, \frac{b_{1}}{b_{2}}$ and $\frac{c_{1}}{c_{2}},$ find out whether the lines representing the following pairs of linear equations intersect at a point,are parallel or coincident:
$6x - 3y + 10 = 0$
$2x - y + 9 = 0$

Solve the following pair of equations by reducing them to a pair of linear equations:
$\frac{1}{3x+y} + \frac{1}{3x-y} = \frac{3}{4}$
$\frac{1}{2(3x+y)} - \frac{1}{2(3x-y)} = -\frac{1}{8}$

Solve the following pair of linear equations by the substitution and cross-multiplication methods:
$8x + 5y = 9$
$3x + 2y = 4$

Use the elimination method to find all possible solutions of the following pair of linear equations:
$2x + 3y = 8$ $...(1)$
$4x + 6y = 7$ $...(2)$

Form the pair of linear equations in the following problems,and find their solutions (if they exist) by the elimination method.
Meena went to a bank to withdraw ₹ $2000$. She asked the cashier to give her ₹ $50$ and ₹ $100$ notes only. Meena got $25$ notes in all. Find how many notes of ₹ $50$ and ₹ $100$ she received.