Question 22114
Compound interest formula:  A = P(1+r/n)^(nt)
A is amount you have now; P is amount you invested; r is annual 
interest rate; n is # of times compounded yearly; t is number of years.
Let "x" be the amount invested and compounded monthly.
Then "4x" is the amount you will have if it reaches 4 times it original value.
So, 4x = x(1+0.093/12)^(12t)
    4  = (1.00775)^12t
Take the log of both sides to get the variable out of the exponent.
log(4) = (12t)(log(1.00775)
Solve for "t":
  t = (1/12)[log4/log(1.00775)]
  t = (1/12)(179.57)
  t = 14.96 years

If compounded continuously the formula is A = Pe^rt
In your case 4x = (x)e^(0.093)t
Take the natural log of both sides after cancelling the "x's" to get:
ln(4) = 0.093t
t = [ln4]/0.093
t = 14.91 years

Cheers,
stan H.