Prove that the exterior angle of a triangle is equal to the sum of two interior opposite angles.

Write all the properties of natural numbers in symbols.

Write the mathematical statements for the given sentence.

The sum of two sides of a triangle is greater than the third side.

Write the mathematical statements for the given sentence.

The sum of two fractional numbers is also a fractional number.

State whether the given statement is true or false. Justify your answer.

The sum of interior angles of a quadrilateral is $350°$.

State whether the given statement is true or false. Justify your answer.

$x^2\ge 0$ for a real number $x$.

State whether the given statement is true or false. Justify your answer.

The sum of two even numbers is always an even number.

State whether the given statement is true or false. Justify your answer.

All prime numbers are odd.