If the point $(a, a-2)$ lies on the graph of the equation $3x + 5y = 30$,find the value of $a$.

If $(2,3)$ is a solution of the equation $7x - 3y = a$ and $(a, a+1)$ is a solution of the equation $2x + y = b$,find the values of $a$ and $b$.

The total cost of $3$ sweetlimes and $6$ oranges is ₹ $210$. Show this statement as a linear equation in two variables.

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.

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 whether the following statement is True or False. Justify your answer:
The graph given below represents the linear equation $x=3$.