The formula of simple interest is: I=PRT Where: I stands for Interest P stands for Price (or Principle Amount) R stands for Rate T stands for Time (in years) I=PRT =7000×0.062×1.5 (6.2%==0.062) (18 months=12 months and 6 months=1.5 year) =$651 $7000+$651=$7651 By the end of 18 months, Mai has $7651 in her account