Hi Gabriella,
10t2 +21t + 6 = 2t
First subtract 2t from both sides so that you have it in the form ax2 + bx + c = 0 (at2 + bt + c = 0 in this case)
Then you can use the quadratic formula. If you proceed correctly you should be able to find a positive perfect square number under the radical part of the equation. The plus and minus feature of the formula should allow you to find two answers, both fractions.
As a hint, the answers you seek are the same as for this equation: (5x + 2)(2x + 3) = 0
If those hints aren't enough, return here with narrower questions.
Enjoy