Question

how much money will betty need, to the nearest cent, to invest in a certificate of deposit to have $20,000 after 20 years if the account earns a simple annual interest rate of 3.5%

Answer 1

I am not sure from which country you are posting but I find it strange that for that length of time simple interest instead of compound interest is used,
nevertheless, with simple interest ....

let the amount invested be x

20000 = x + 20(.035)x
20000= x(1 + .7)
x = 11764.70

had it been compounded ....
20000 = x(1.035)^20
x = 10051.31