1. **State the problem:** We are given the sequence formula $a_n = 20n - 30$ and asked to find the term $a_{31}$. 2. **Formula used:** The formula for the $n$-th term of the sequence is $a_n = 20n - 30$. 3. **Substitute $n=31$ into the formula:** $$a_{31} = 20 \times 31 - 30$$ 4. **Calculate the multiplication:** $$a_{31} = 620 - 30$$ 5. **Perform the subtraction:** $$a_{31} = 590$$ 6. **Final answer:** The 31st term of the sequence is $590$.