Math Finance
posted by Clara .
How much interest does $2560 earn in 17 months at a rate of 5 1/8 ?

I assume you mean simple interest at an annual rate of 5 1/8 %
5 1/8 % = 0.05125
17 months = 17/12 years.
$2560 * .05125 * 17/12 = $185.87 
joan wants to start an IRA that will have $250,000 in it when she retires in 18 years. How much should she invest nnually in her IRA to do this if the interest is 4% compounded annually round to the nearest cent