In a two-digit number,the digit at the unit's place is $(x+1)$ and the digit at the ten's place is $(x+2)$,then that number is $\ldots \ldots \ldots \ldots .$

Solve the following pair of equations by the cross-multiplication method:
$ax - by = \frac{a-b}{2}$
$x + 3y = 2$

Solve the following pair of linear equations in two variables using a graph: $4x + y = 7$ and $16x + 4y = 28$.

Solve the following pair of linear equations by the method of substitution: $2x - y + 3 = 0$ and $y = 2x - \frac{3}{2}$.

$A$ railway half ticket costs half the full fare,but the reservation charges are the same on a half ticket as on a full ticket. One reserved first class ticket from station $A$ to $B$ costs $Rs. 2530$. Also,one reserved first class ticket and one reserved first class half ticket from $A$ to $B$ costs $Rs. 3810$. Find the full first class fare from station $A$ to $B$,and also the reservation charges for a ticket (in $Rs.$).

Solve the following pair of linear equations using a graph: $3x + 6y = 3900, x + 3y = 1300$