Answer:
Solution 1:
Simple Interest = Principle × Rate × Time
Time = Simple Interest / Principle × Rate
Presently, all together for introductory venture of $98,000 to reach $181,000 = $83,000 of premium should be earned
$83,000 = $98,000 * 6.6% * n
n = 12.83 years
Solution 2:
For self multiplying dividends,

Presently the aggravating occurs on month to month premise,
So,
r = 6.6% / 12
r = 0.55% (Monthly);

Taking log of the two sides,
LN(1.8469) = n * LN(1.0055)
0.6135 = n * 0.005485
n = 111.86 months
n = 111.86/12
n = 9.32 years