In a two-digit number,the digit at unit's place is $x$ and the digit at ten's place is $y$. The number obtained by interchanging the digits is ...........

If $5x + 3y = 10xy$ $(x \neq 0, y \neq 0)$,then $\frac{6}{x} + \frac{10}{y} = ...........$

For the linear equation in two variables $3x + 2y = 8$,if the value of $x$ is $-2$,then $y = \dots$

If $x=a$ and $y=b$ is the solution of the equations $x-y=2$ and $x+y=4,$ then the values of $a$ and $b$ are,respectively:

The ages of two girls are in the ratio $5:7$. Eight years ago,their ages were in the ratio $7:13$. Represent this situation as a pair of linear equations in two variables.

The cost of $2\,kg$ of apples and $1\,kg$ of grapes on a day was found to be Rs. $160$. After a month,the cost of $4\,kg$ of apples and $2\,kg$ of grapes is Rs. $300$. Represent this situation as a pair of linear equations in two variables.