-logt=0.064 t?

Here is the graph that Bertie is talking about:)

https://www.desmos.com/calculator/ji4yx6xxwv

This is a non-linear equation, and requires a numerical method for its solution, Newton-Raphson for example.

A simple sketch graph (y = log(x) and y = -0.064x), shows that there is a single root and that its value will be slightly less than 1.

Rather than use a numerical method, you could simply use one of those clever graph plotters.

The root turns out to be 0.87856 5dp.