Answer:
3^2
Explanation:
a^b^c = a^(b*c)
a^b * a^c = a ^ (b+c)
Lets break down each piece
81^2 = (9*9)^2 = (3^2 *3^2) ^2 = (3^4)^2 = 3^8
9^3 = (3^2) ^3 = 3^(2*3) = 3^6
27^4 = (3*9)^4 = (3*3^2)^4 = (3^(1+2))^4 = (3^3)^4 = 3^3^4 = 3^(3*4) = 3^12
Putting this back into the fraction
3^8 * 3^6
-------------------
3^12
3^(8 +6)
-------------------
3^12
3^14/3^12
a^b/a^c = a^(b-c)
3^(14-12)
3^2