The side faces of a pyramid are:

In the Book of Elements $1$,how many definitions are given?

Solve the following question using an appropriate Euclid's axiom:
In the figure:
$AB = BC$,$M$ is the mid-point of $AB$ and $N$ is the mid-point of $BC$. Show that $AM = NC$.

Solve the following question using appropriate Euclid's axiom:
Two salesmen make equal sales during the month of August. In September,each salesman doubles his sale of the month of August. Compare their sales in September.

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

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