For a given arithmetic series $u_n,$ it is known that the $3^{\text{rd}}$ term is $2$ and the sum of the first thirty terms is $-1815.$

What is the ${10}^{\text{th}}$ term of this sequence?

Let $u_n=a+(n-1)d$ and $$\begin{gathered} S_n=\frac{n}{2} \\ left[2a+(n-1)d \\ right] \end{gathered}$$.

You know $u_4$ and $S_{30}$ - this enables you to find $a$ and $d.$

Once you know $a$ and $d,$ you can find $u_{10}$ using the formula for the $n^{\text{th}}$ term.