Answer:
90
Step-by-step explanation:
The degree measure of a line is (180) degrees. As per the given picture, angles (a), (b), and the (90) degree angle form a straight line. Please note that an angle with a box around it is always a (90) degree angle.
Using the given information, one can form an equation and solve for the sum of angles (a) and (b);
a + b + 90 = 180
Inverse operations,
a + b = 90
