The standard form of $2x = 5y$ is............

Find the value$(s)$ of $p$ for the pair of equations $2x + 3y - 5 = 0$ and $px - 6y - 8 = 0$ if the system has a unique solution.

Students of a class are made to stand in rows. If $1$ student is extra in a row,there would be $2$ rows less. If $1$ student is less in a row,there would be $3$ rows more. Find the total number of students in the class.

Solve the following pair of equations by the method of cross multiplication:
$x + y - (a + b) = 0$
$ax - by - (a^2 - b^2) = 0$

The sum and difference of the reciprocals of the ages of a son and father are respectively $\frac{5}{40}$ and $\frac{3}{40}$. Represent this as a pair of linear equations in two variables,where $x$ is the age of the son and $y$ is the age of the father.

Pathik travels $600 \, km$ to his home partly by train and partly by car. He takes $8$ hours if he travels $120 \, km$ by train and the rest by car. He takes $20$ minutes longer if he travels $200 \, km$ by train and the rest by car. Find the speed of the train and the car.