1. **State the problem:** We have an arithmetic sequence representing the number of toy rockets produced each hour for 8 hours. The first hour's production is 40 rockets, and the second hour's production is 43 rockets. We need to find the number of rockets produced in hour seven. 2. **Recall the formula for an arithmetic sequence:** $$a_n = a_1 + (n-1)d$$ where $a_n$ is the number of rockets produced in the $n$th hour, $a_1$ is the first term, and $d$ is the common difference. 3. **Find the common difference $d$:** Given $a_1 = 40$ and $a_2 = 43$, $$d = a_2 - a_1 = 43 - 40 = 3$$ 4. **Calculate the number of rockets produced in hour seven ($a_7$):** $$a_7 = a_1 + (7-1)d = 40 + 6 \times 3$$ $$a_7 = 40 + 18 = 58$$ 5. **Answer:** The assembly line will produce **58 rockets** in hour seven.