Dr. Lizardo writes down a sequence of $n$ letters, where each letter is A, B, or C, and the letter A appears an even number of times. How many different sequences could Dr. Lizardo have written down?

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

If angle b measures 25°, what is the approximate perimeter of the triangle below? 10.3 units 11.8 units 22.1 units 25.2 units

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)