Write the next three terms of the arithmetic sequence. 4,3 3/4, 3 1/2, 3 1/4, blank, blank, blank.

Igot the answer of 15.8 years.

Use pythagorean’s theorem and find the missing side lengths of the two smaller triangles and add them together
13^2 - 12^2 = 5
15^2 - 12^2 = 9
5+9 = 14
14 is the length of each side of the square
14^2 + 14^2 = 19.8
19.8 is the diagonal length of the inside if the square