$x$ is larger in two numbers $x$ and $y$. Two times the larger number is $4$ more than five times the smaller number. The equation form of this data is $\ldots \ldots \ldots \ldots$

The sum of the digits of a two-digit number is $6$. The number obtained by interchanging the digits is $18$ less than the original number. Find the original number.

Places $A$ and $B$ are $90\, km$ apart from each other on a highway. $A$ car starts from $A$ and another from $B$ at the same time. If they move in the same direction,they meet in $9$ hours and if they move in opposite directions,they meet in $\frac{9}{7}$ hours. Find the speeds of the cars.

$x$ years ago,the age of Mahesh was $y$ years. Then,after $z$ years,his age will be $\ldots$ years.

If a pair of equations $3x + ky - 9 = 0$ and $x + 2y - 3 = 0$ has infinite solutions,then $k = \ldots$

Write an equation of a line passing through the point representing the solution of the pair of linear equations $x+y=2$ and $2x-y=1$. How many such lines can we find?