Question

Betty invested some money at 15% interest. Betty also invested $⁢237 more than 2 times that amount at 13% . How much is invested at each rate if Betty receives $⁢1688.03 in interest after one year? (Round to two decimal places if necessary.)

Answer 1

Let x represent the amount Betty invested at 15%. The (2x+237) is the amount Betty has invested at 13%. Her total earnings are ...
x*0.15 + (2x+237)*0.13 = 1688.03
0.41x + 30.81 = 1688.03
x = (1688.03 -30.81)/0.41 = 4042.00

Betty has $4042.00 invested at 15%.
Betty has $237 +2*4042 = $8321.00 invested at 13%.