Write four solutions for the equation: $x = 4y$

Give the geometric representations of $2x + 9 = 0$ as an equation
$(i)$ in one variable
$(ii)$ in two variables

In countries like $USA$ and Canada,temperature is measured in Fahrenheit,whereas in countries like India,it is measured in Celsius. Here is a linear equation that converts Fahrenheit to Celsius:
$F = \left(\frac{9}{5}\right) C + 32$
$(i)$ Draw the graph of the linear equation above using Celsius for $x$-axis and Fahrenheit for $y$-axis.
$(ii)$ If the temperature is $30\,^oC$,what is the temperature in Fahrenheit?
$(iii)$ If the temperature is $95\,^oF$,what is the temperature in Celsius?
$(iv)$ If the temperature is $0\,^oC$,what is the temperature in Fahrenheit and if the temperature is $0\,^oF$,what is the temperature in Celsius?
$(v)$ Is there a temperature which is numerically the same in both Fahrenheit and Celsius? If yes,find it.

The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement. (Take the cost of a notebook to be Rs. $x$ and that of a pen to be Rs. $y$).

Draw the graph of the linear equation in two variables: $x - y = 2$.

You know that the force applied on a body is directly proportional to the acceleration produced in the body. Write an equation to express this situation and plot the graph of the equation.