The solution set of a pair of equations $x+y-2=0$ and $2x+2y-4=0$ is $\ldots \ldots \ldots . . . .$

There are some students in the two examination halls $A$ and $B$. To make the number of students equal in each hall,$10$ students are sent from $A$ to $B$. But if $20$ students are sent from $B$ to $A$,the number of students in $A$ becomes double the number of students in $B$. Find the number of students in the two halls.

The general form of a linear equation in two variables is .......... (where,$a^{2}+b^{2} \neq 0$).

The solution set of $x+y-1=0$ and $3x+3y-2=0$ is ...........

Solve the following pair of linear equations:
$21x + 47y = 110$
$47x + 21y = 162$

For a pair of equations $7x - 13y = 1$ and $13x - 7y = 19$,find the value of $x - y$.