i) 1.25(10^17)

ii) 12.5(10^-12)

iii) 0.125(10^-12)

This is what I did.

i) 1.25(10^17) = 125(10^15) = [5(10^5)]^3, then x = 500000

ii) 12.5(10^-12) = 125(10^-13) = [5(10^-13/3)]^3, then x = 0.00023207...

iii) 0.125(10^-12) = 125(10^-15) = [5(10^-5)]^3, then x = 0.00005

I answered only i since 0.00005 is not an integer, but the answer key says it is i and iii. Is the answer key wrong or am I missing something?