If 11,100 is invested at 3.1 percent interest compounded monthly, how much will the investment be worth in 19 years?

The formula for compound interest is:
A=P(1+r/n)^(nt)
Where A represents the amount of money in the account after t years, P is the principal (investment), n is the number of compoundings per year, and r is the interest rate in decimal form.
P=11,100
r=.031
n=12 (monthly)
t=19
A=11,100(1+.031/12)^(12*19)
A=11,100(1+. 002583)^(228)
A=11,100(1.002583)^(228)
A=11,100(1.80082)
A=$19,989.10

3(m+3) = 3m -  9

3m+9 = 3m-9

9 = -9???

clearly, this does not work, so there are NO SOLUTIONS.

Let me know  if this helps!