What is the base of the absolute temperature scale?

The study of physical phenomena at low temperatures (below liquid nitrogen temperature) is called:

$A$ new temperature scale uses $X$ as a unit of temperature,where the numerical value of the temperature $t_x$ in this scale is related to the absolute temperature $T$ by $t_x = 3T + 100$. If the specific heat of a material using this unit is $1400 \, J \, kg^{-1} X^{-1}$,its specific heat in the $SI$ system of units is:

The temperature of a body on the Kelvin scale is $x \ K$. When the temperature of this body is measured with a Fahrenheit thermometer,it is found to be $x \ ^\circ F$. Then $x = $......

On a temperature scale $X$,the boiling point of water is $65^{\circ} X$ and the freezing point is $-15^{\circ} X$. Assume that the $X$ scale is linear. The equivalent temperature corresponding to $-95^{\circ} X$ on the Fahrenheit scale would be $..........^{\circ} F$.

On a new temperature scale, the melting point of ice is $20^{\circ} X$ and the boiling point of water is $110^{\circ} X$. $A$ temperature of $40^{\circ} C$ would be indicated on this new temperature scale as (in $^{\circ} X$)