Question

solve for a. a = ?°

Explanation:

Step1: Recall angle - sum property of a triangle

The sum of interior angles of a triangle is 180°. Let the third - interior angle of the triangle be $x$. So, $x+25^{\circ}+30^{\circ}=180^{\circ}$.

Step2: Solve for the third - interior angle $x$

$x = 180^{\circ}-(25^{\circ}+30^{\circ})=180^{\circ}-55^{\circ}=125^{\circ}$.

Step3: Use the linear - pair property

The angle $a$ and the interior angle $x$ form a linear pair. Since the sum of angles in a linear pair is 180°, and $x = 125^{\circ}$, then $a+125^{\circ}=180^{\circ}$.

Step4: Solve for $a$

$a=180^{\circ}-125^{\circ}=55^{\circ}$.

Answer:

$55$