Yeah not just one letter but two letters perpendicular to another two letters. Each 2 letters like AB is a straight line which is crossed by another 2 letters making it perpendicular.
The answer is 4.5 for the side length of the pentagon and 7.5 is the side length for the triangle because 7.5*3(3 sides) = 22.5 and 4.5*5(5 sides)= 22.5. The perimeter is 22.5
