Substitution of \(\displaystyle u = \frac{t}{60}\\) gives:
\(\displaystyle 6u - e^u + 4 = 0\)
Then I'd plot the curve y = 6u - e^u + 4 and see where it touches the x-axis, then multiply the result by 60 to find an approximate value for t. Or you could use other numerical methods. Just from looking at it, I'd hazard a guess at u being negative, hence t being a smaller negative number.