Ariane borrows $600 on a 2−year loan. she is charged 5% simple interest per year. how much interest is she charged for 2 years? what is the total amount she has to pay back?

Find out what 5% of $600 is by multiplying them by each other after changing the percent from a percentage form into a decimal.
600*.05=$30
Now add that to $600 every year. 
$600+$30=630.
Now add it again since it's for two years. 
$630+$30= $660. 
$660.

I’m confused as to what you are asking 66 2/3 percentage wise