This question involves rearranging equations. In this case we need to get t on the LHS (left hand side) of this equation in order to find an expression for t. An expression for t just means, what does t equal?Taking the natural log of both sides of this equation we have;ln(e4t)=ln(6)The natural log is the inverse function of 'e' so the above reduces to4t = ln(6)which we can rearrange to findt= (ln(6))/4