Five years ago,the sum of the ages of five persons was $50$ years. After five years,the sum of the ages of those five persons will be $\ldots \ldots \ldots \ldots$ years.

Draw the graphs of the pair of linear equations $x+3y=6$ and $2x-3y=12$. Determine the coordinates of the vertices of the triangle formed by these linear equations and the $Y$-axis.

The two-digit number whose digit at the unit's place is $x$ and the digit at the ten's place is $y$ is three times the sum of its digits. This statement is written as $\ldots \ldots \ldots \ldots .$

There are some $25$ paise coins and some $50$ paise coins in a bag. The total number of coins is $150$ and the amount in the bag is Rs. $55$. Find the number of coins of each value in the bag.

Solve the following pairs of equations:
$\frac{2xy}{x+y} = \frac{3}{2}$
$\frac{xy}{2x-y} = \frac{-3}{10}, \quad x+y \neq 0, 2x-y \neq 0$

For a pair of equations $5x - 4y = 1$ and $10x = 8y + 2$,in usual notations $a_{1}b_{2} - a_{2}b_{1} = \dots$