The graph of $x+y=0$ passes through the origin and which quadrants?

State whether the following statement is true or false:
If $(5, -2)$ is a solution of $5x + 2y = k$,then $k = 0$.

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

One of the solutions of the linear equation $3x + 5y = 30$ is $\ldots \ldots . .$

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.

Express the following linear equation in the form $ax + by + c = 0$ and indicate the values of $a, b$ and $c$ in each case: $6x - 5y = 4.2\overline{7}$