A and B are regular octagons. The scale factor of A to B is 2:4. the perimeter of octagon A is 64 in.

Perimeter is 128 in, length of each side is 16 in

Step-by-step explanation:

2 : 4 = 1 : 2

Perimeter is the sum of sides.

Ratio of the perimeters is the same ratio as of the sides.

side A : side B = 1 : 2

Perimeter A : Perimeter B = 1 : 2

Perimeter of Octagon B is 2×64 = 128 in

With each side equal to 128/8 = 16 in

the sum of all the angles in a triangle are equal to 180

so you can add   the 3 given angles together to equal 180:

5y + 2y + 2y = 180

or since all three angles have the same letter, combine the 3 angles to equal 180:

9y = 180

y=mx+b is the final answer!   : )