(2a-^5×a-²/a²)-³=.................

(2a^-5×a-²/a²)-³=2-³ × a^15 × a^6/a^-6
= a^15 × a^6 × a^6 per 2³
= a^27 /8

(2a^-5 × a^-2/a^2)^-3
= (2a^(-5-2-2))^-3
= (2a^-9)^-3
= 2^-3 . a^(-9×-3)
= 1/2^3 . a^27
= 1/8 . a^27
= a^27/8