You have to write "using System;" at the beginning of your code.

If John starts out with $10,000 and withdraws $10,000 per year, how in God's green earth can he last 2 years?
I'm 62 years old and retired (just do this for fun), so I better get this right! (or else I'm %&#@ed!)

I pass all the test except this one. I must have a thick head because I don't see it.
I mean, if I start out with $10,000 and use up $10,000 per year, how can I possibly
last 2 years?

check your code for "Boolean" instead of "boolean" would be my guess

This one doesn't appear to be working properly for me.

I get this hard error and can't seem to fix it.
src/Solution.cs(3,19): error CS0246: The type or namespace name 'Boolean' could not be found (are you missing a using directive or an assembly reference?)