t = 18.12

15,000 = 10,000(1 + 0.0725)^t

15,000 = 10,000(1 + 0.0525)^t

t = 6.69

15,000 = 5,000(1 + 0.0525)^t

15,000 = 10,000(1 + 0.0625)^t

15,000 = 5,000(1 + 0.0625)^t

t = 15.7

t = 7.92

15,000 = 5,000(1 + 0.0725)^t

t = 21.47

t = 5.79