Calculating Ksp from ion concentrations

[mister_mister3]

In the expression:

ksp = (3.42 x 10^-7) (6.84 x 10^-7)^2
= 1.6 x 10^-19

I don't understand how the final answer is found. Can someone show me a step by step? I'm attempting to understand how to do these types of questions! Any help is greatly appreciated!

 

[vsage]

You're having trouble multiplying the exponents? I have a feeling you didn't ask the entire question.