Your sum is 627. You do have to regroup because u have get a double digit and you have to bring it up.
Where is the picture of figure 12?
20 goes into 75
3x's
20 40 60 with only 15 left over
Use the formula for simple interest:
i = p*r*t
Then i = ($828.75)(0.065)(1.5)
= $80.80
6.5% must be converted to a decimal fraction: 0.065, and 18 months to years, specifically 1.5 years.