For the equation $F = (9/5)C + 32$,$F$ and $C$ are numerically equal when $F = \ldots$

Let $y$ vary directly as $x$. If $y=12$ when $x=4$,then write a linear equation. What is the value of $y$ when $x=5$?

For what value of $c,$ the linear equation $2x + cy = 8$ has equal values of $x$ and $y$ for its solution?

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.

$...$ is not a point on the graph of $3x + 2y = 18$.

Check whether the point $(\sqrt{2}, 4\sqrt{2})$ is a solution of the equation $x - 2y = 4$.