The amount of Tina money can be expressed in an exponent function like this:
an= $1100(1.0725)^n
The variable an represent the total money and variable n is the years needed to achieve that amount.
Then, the time needed for the money to reach $6,600 would be:
an= $1100(1.0725)^n
$6,600= $1100(1.0725)^n
$1,100(6)= $1100(1.0725)^n
6= (1.0725)^n
n= log1.075 6
n= 24.78