To find the measure of the missing angle $a$, we need to recognize that the given angles form a linear pair. A linear pair of angles is formed when two angles are adjacent (next to each other) and their non-common sides form a straight line. The sum of the angles in a linear pair is always $180^\circ$.

Given:

• One angle is $93^\circ$.
• The other angle is $a$ (the missing angle).

Since the sum of the angles on a straight line is $180^\circ$, we can write:

$a + 93^\circ = 180^\circ$

To solve for $a$:

$a = 180^\circ - 93^\circ$

$a = 87^\circ$

So, the measure of the missing angle $a$ is $87^\circ$.

Would you like more details or have any questions? Here are some related questions you might find helpful:

1. What are linear pairs of angles and how do they relate to supplementary angles?
2. How do you identify complementary and supplementary angles?
3. What is the difference between adjacent angles and linear pairs?
4. Can two obtuse angles form a linear pair? Why or why not?
5. How do angle relationships change when dealing with parallel lines cut by a transversal?

Tip: Remember, the sum of angles forming a straight line is always $180^\circ$. This is a key concept in geometry, especially when working with linear pairs or supplementary angles.