Solve the following question using appropriate Euclid's axiom:
It is known that $x+y=10$ and that $x=z$. Show that $z+y=10$.

Consider the following statement: "There exists a pair of straight lines that are everywhere equidistant from one another." Is this statement a direct consequence of Euclid's fifth postulate? Explain.

State whether the following statement is True or False. Justify your answer.
The boundaries of the solids are curves.

If a straight line falling on two straight lines makes the interior angles on the same side of it,whose sum is $120^{\circ}$,then the two straight lines,if produced indefinitely,meet on the side on which the sum of angles is

The things which are double of the same thing are

Solve the following question using an appropriate Euclid's axiom:
In the figure,$X$ and $Y$ are the mid-points of $AC$ and $BC$ respectively,and $AX = CY$. Show that $AC = BC$.