Answer: 47.8 years
Explanation:
Jack is trying to make up to $330,000 from $50,680 at a rate of 4%.
The relevant formula is the future value formula as Jack is trying to get to a certain amount in future:
330,000 = 50,680 * ( 1 + 4%) ^ number of years
1.04 ^ number of years = 330,000 / 50,680
1.04 ^ N = 6.51144435674822
Use the natural logarithm:
N * In (1.04) = In (6.51144435674822)
N * 0.039220713153281 = 1.873561299007586979
N = 1.873561299007586979 / 0.039220713153281
= 47.8 years