P is the principal amount, $3500.00.
r is the interest rate, 10% per year, or in decimal form, 10/100=0.1.
t is the time involved, 5....year(s) time periods.
So, t is 5....year time periods.
To find the simple interest, we multiply 3500 × 0.1 × 5 to get that:The interest is: $1750.00
If you need compounding the formula is different.