point: A point is a dot in a plane or a piece of paper. A point does not have any length, width or height. It determines the location or position in a plane. Put a dot on a paper and mark it as A or with any capital letter, to show a point.

line: A line is a figure formed when two points are connected with minimum distance between them, and both the ends extended to infinity. While lines have no definite beginning or end, they are represented in our day-to-day lives with examples such as railway tracks or the freeway.

ray: a line with a single endpoint (or point of origin) that extends infinitely in one direction.

line segment: a part of a straight line that is bounded by two distinct endpoints (its extreme points), and contains every point on the line that is between its endpoints.

plane: the geometrical concept of a flat surface with no edges or thickness. In other words, a plane is a flat surface that only exists in two dimensions and extends infinitely in those dimensions.

angle: formed by two lines that meet at a point. Each line is called a side of the angle, and the point they share is called the vertex of the angle.

acute: Acute angles are smaller than 90°.

obtuse: Obtuse angles are larger than 90°, but less than 180°

right angle: A right angle is an angle that measures 90 degrees.

straight angle: A straight angle measures 180° and looks like a straight line, therefore, it is a mathematical way of expressing a straight line. It is an angle whose arms lie in opposite directions from the vertex and they join together to form 180°. Let us learn more about the straight angle in this article.

segment addition postulate: The Segment Addition Postulate is a fundamental principle in geometry that states that if three points A, B, and C are collinear such that B lies somewhere on AC, then the sum of the lengths of the segments AB and BC is equal to the length of the entire segment AC.

angle addition postulate: The Angle Addition Postulate states that the sum of two angle measures that are joined by a common ray will be equal to the measure of the angle they form. The two angles that are joined by a common ray are called adjacent angles.

How to solve this:

A straight line measures 180°. The two angles are adjacent, meaning they share a side. Together, they make up a straight line. In other words, they are a linear pair.

   a + 53 =180

Equivalently:

a = 180 - 53

a = 127

                                                                                                Answer: 127