The answer is (rounded to the nearest tenth) about 5.7 and since neither 18 or 2 have a perfect square, so this is irrational.
Perimeter: 26
Area: 32
Let me know if you need me to explain in depth!!
If my calculations are correct , only 26 stacks of folders will only hold 7 folders evenly .. leaving 1 pile with 9 folders because 26*7= 182 & 184-182 = 2 . 7+2=9
Do you know the numbers a/b equals too