Please check my answer:

Place the numbers in descending order.

2.3 × 10−10 ; 3.2 × 10−10 ; 2.3 × 10−12 ; 2.3 × 10−8...

(2.3 × 10^-8 ; 3.2 × 10^-10 ; 2.3 × 10^-10 ; 2.3 × 10^-12)

Your answer is correct! The numbers in descending order are:

2.3 × 10^-8
3.2 × 10^-10
2.3 × 10^-10
2.3 × 10^-12