Write out more steps, and check the details. You have one sign error.
Also, when you check your answer using the number you found (which was an excellent thing to do), don't use the rounded answer they asked for; use a more accurate value to avoid rounding errors: 0.8333333, or the entire value stored in your calculator.
Now, when I use the calculated value in your inverse, I get t = -3, which makes the sign error obvious. When I use 0.83, I get -0.92, which is very, very different. Clearly this equation is highly sensitive, and rounding to 2 decimal places is not a good idea!