Write the linear equation such that each point on its graph has an ordinate $3$ times its abscissa.

The total cost of a school picnic consists of two parts: a fixed bus fare of ₹ $200$ and the cost of snacks at the rate of ₹ $30$ per student. Representing the total number of students by $x$ and the total cost by $y$,form a linear equation in two variables. If the number of students going on the picnic is $40$,find the total cost.

Write four solutions for the following equation: $2x + 3y = 7$.

If the graph of the equation $3x + ay = 7$ passes through the point $(3, -1)$,then the value of $a$ is:

The work done by a body on application of a constant force is the product of the constant force and the distance travelled by the body in the direction of force. Express this in the form of a linear equation in two variables and draw its graph by taking the constant force as $3$ units. What is the work done when the distance travelled is $2$ units? Verify it by plotting the graph.

For the equation $5x + 3y = 90$,if $x = 12$,then $y = \dots$