In order to solve for t, where t is an exponent, you must take the ln of each side of the equation. It also works to take the log of each side--exactly the same answer!
This should bring back the laws of logarithms, in which the exponent becomes the coefficient:
Finally divide both sides by ln(1.06), and calculate with a calculator:
= 6.958515, which rounds off to about 6.96.