Find the value of $k$,if $x = 2$,$y = 1$ is a solution of the equation $2x + 3y = k$.

Check whether $(4, 0)$ is a solution of the equation $x - 2y = 4$.

Write four solutions for the equation: $\pi x + y = 9$

Express the following linear equation in the form $ax + by + c = 0$ and indicate the values of $a$,$b$,and $c$: $-2x + 3y = 6$.

If the work done by a body on application of a constant force is directly proportional to the distance travelled by the body,express this in the form of an equation in two variables and draw the graph of the same by taking the constant force as $5$ units. Also,read from the graph the work done when the distance travelled by the body is:
$(i)$ $2$ units
$(ii)$ $0$ units

Write each of the following as an equation in two variables:
$(i)$ $x = -5$
$(ii)$ $y = 2$
$(iii)$ $2x = 3$
$(iv)$ $5y = 2$