In mathematics, this is a type of statement which can be proven.
What is a theorem?
In Euclidean geometry, there exist this many lines parallel to a given line and through a given point not on that line.
What is 1?
This is the full name of the often-abbreviated HL theorem.
What is the hypotenuse-leg theorem?
This is the partition postulate of inequality, in words.
What is a whole is greater than any of its parts?
Given the parallelogram in the diagram below, compute the tuple (x,y).
In mathematics, this is a type of statement which is accepted as truth without proof.
What is a postulate?
This is a pair of same-side interior angles in the diagram below.

What is angle 4 and angle TSA?
This is what the infamous acronym CPCTC stands for?
What is corresponding parts of congruent triangles are congruent?
This is the longest line segment in the diagram below.

What is segment WY?
These three special types of quadrilaterals all must have perpendicular diagonals.
What are the kite, the rhombus, and the square?
A line has this many dimensions.
What is 1?
This is the missing condition in the following definition:
Two lines are parallel iff they never meet.
What is coplanar?
Given triangle MON is congruent to triangle TUE, this is a pair of sides (one from each triangle) which is not necessarily congruent.
What is MO and UE, ON and ET, NM and TU, etc.?
This is the exterior angle theorem of inequality, in words.
What is the measure of an exterior angle drawn to a triangle is greater than the measure of either non-adjacent interior angle.
This special type of quadrilateral may or may not be a parallelogram, but, if it is, then it must be a rectangle.
What is an isosceles trapezoid?
Where two lines meet, this many distinct linear pairs (of angles) are formed.
What is 4?
Only considering the numbered angles, this is how many distinct pairs of corresponding angles are in the diagram below. 
What is 6?
This is can be said about the set of all points on the perpendicular bisector of a particular line segment.
What is they are equidistant from the endpoints of the segment?
If two sides of a triangle have lengths x+3 and x-5, then this is the minimum integer length of the third side.
What is 9?
In kite ABCD, AB=4.4 and BC=7.2. This is the perimeter of ABCD.
What is 23.2?
This is a geometric relation which does not satisfy the transitive property.
What is "is perpendicular to", "is complementary to", "is supplementary to", "is adjacent to", etc.?
Given some triangle ABC, this is the first step in the classic proof of the triangle sum theorem.
What is draw a line through one vertex parallel to the opposite side?
This is the one case in which an altitude must be drawn outside a triangle (to the line containing the opposite side, not the side itself).
What is drawn from the vertex of an acute angle in an obtuse triangle?
This is how many isosceles triangles have all integer side lengths and a perimeter of 25.
What is 6?
Given ABCD is a parallelogram, compute the tuple (x,y,z).

What is (56,39,85)?