1. **State the problem:** Elvin starts with 90 comic books. He donates one third of them to a library, then buys 4 comic books at each of 6 bookstores. We want to find an expression for the number of comic books Elvin has after these transactions. 2. **Write the expression for donation:** One third of 90 is calculated as $$\frac{1}{3} \times 90 = 30$$. This means Elvin donates 30 comic books. 3. **Calculate remaining comic books after donation:** Subtract the donated books from the original amount: $$90 - 30 = 60$$. 4. **Calculate the number of comic books bought:** Elvin buys 4 comic books at each of 6 bookstores, so total bought is $$6 \times 4 = 24$$. 5. **Calculate total comic books after buying:** Add the bought comic books to the remaining ones: $$60 + 24 = 84$$. **Final expression:** $$90 - \frac{1}{3} \times 90 + 6 \times 4$$ **Final answer:** Elvin has 84 comic books after these transactions.