N3
21×21^7/21^6 - 3^5×6^5/18^3= 21^8/21^6 - 3^5×(2×3)^5/(3^2×2)^3=21^2 - 3^5×2^5×3^5/3^6×2^3=21^2 - 3^10×2^5/3^6×2^3=21^2-(3^4×2^2)=(3×7)^2-(3^4×2^2)=3^2×7^2-((3^2)^2×2^2=3^2×(7^2-(3^2×2^2))=9×(49 ×(9×4))=9×13=117
N4
(X^7) ^3 × (x^3) ^9÷(x^4)^6 / x^23=4112
X^21×x^27÷x^24/x^23=4112
X^24/x^23=4112
X=4112
N5
В порядке возрастания: (-1, 3)^3; 2^0; (-1, 1)^2; (2, 4) ^4; (4, 7)^4; (-5)^4