Question

$500 invest at 4% simple interest for 3 years

Answer 1

500x4%x3=60 the answer is $60

Answer 2

Simple interest formula:
I=Prt  where I = interest p=principle and r and A=P(1+rt)  where A = the amount accumulated over t years.
plug in your values 
principle=  500
r=.04
t=3
A=300(.04)(3)
A=$545