Answer:
24 years
Step-by-step explanation:
Total = start*(1 + interest rate / amount of times compounded per month)^(years*amount of compounds per year)
6000 = 3000*(1+0.03/4)^(4x)
6000 = 3000* ((403/400)^4)^x
2 = ((403/400)^4)^x
x = log base-((403/400)^4) of 2 = x
x = 23.19
rounding down 23 years (but you probably want a year over that to get at least 6000, so 24)
