A family is comparing different car seats. One car seat is designed for a child up to and including 2626 lb. Another car seat is designed for a child between 2020 lb and 4040 lb. A third car seat is designed for a child between 2626 lb and 9090 ​lb, inclusive. Model those ranges with compound inequalities. Which car seats are appropriate for a 3030​-lb ​child?

Let's denote the weight of the child as \( x \) in pounds. We can model the weight ranges for each car seat using compound inequalities.

1. **First Car Seat:** Designed for a child up to and including 2626 lb.
\[
x \leq 2626
\]

2. **Second Car Seat:** Designed for a child between 2020 lb and 4040 lb.
\[
2020 \leq x \leq 4040
\]

3. **Third Car Seat:** Designed for a child between 2626 lb and 9090 lb, inclusive.
\[
2626 \leq x \leq 9090
\]

Now, let's evaluate which car seats are appropriate for a child weighing 3030 lb.

- For the **first car seat**: \( 3030 \leq 2626 \) is **false**, so this car seat is **not appropriate**.

- For the **second car seat**: \( 2020 \leq 3030 \leq 4040 \) is **true**, so this car seat is **appropriate**.

- For the **third car seat**: \( 2626 \leq 3030 \leq 9090 \) is **true**, so this car seat is **appropriate**.

In summary, the **appropriate car seats for a 3030-lb child are the second and third car seats**.