Answer
$t=-3\pm\sqrt{7}$
Work Step by Step
$(t+3)^{2}=7$
According to the general principle of square roots:
For any real number $k$ and any algebraic expression $x$ :
$\text{If }x^{2}=k,\text{ then }x=\sqrt{k}\text{ or }x=-\sqrt{k}$.
$ t+3=\pm\sqrt{7}\qquad$... add $-3$ to both sides.
$t=-3\pm\sqrt{7}$
