If <a is 89.5, what is the measure of its complementary angle?​

The complement of an angle is what, when added to it, equals 90 degrees (90°). For example, in your problem, 90°-85°=5°. This means that the complement of 85° is 5°, since they add up to equal 90 degrees a right angle.

The supplement of an angle is what, when added to it, equals 180 degrees.

For example, in your problem, 180°-85°=95°. This means that the supplement of 85° is 95°, since they add up to equal 180 degrees a straight angle.