Answer: The measure of <b is 26 degrees.
Step-by-step explanation:
Complementary angles are angles that add up to 90 degrees. I remember this because my teacher told me this: "Complements are always RIGHT!" Of course, this is a reference to complementary angles combining to make right angles, which are 90 degrees.
To go back on your question, if <a and <b are truly complementary, then m<a +m<b = 90 degrees. Substitute the measure of <a for 64 degrees, then you get 64 degrees + m<b = 90 degrees. Simplify. Then you'd get that the measure of <b is 26 degrees.
(P.S. Sorry if I cluttered up the ask portion of your post. I haven't used this platform in like 2 years, so everything seems so foreign to me.)