Define the set C = x ∈ ℝ | -2 ≤ x < -1 using interval notation.

Set C is defined as the set of all $x$ such that $x$ is a real number ($\mathbb{R}$) and $x$ is greater than or equal to -2 and less than -1.

$$C = \{x \in \mathbb{R} \mid -2 \leq x < -1\}$$

The condition $-2 \leq x$ means that the interval includes the endpoint -2. This is represented by a square bracket [.
The condition $x < -1$ means that the interval does not include the endpoint -1. This is represented by a parenthesis ).
Combining these, the interval is from -2 (inclusive) to -1 (exclusive).

$$C = [-2, -1)$$

The set C is the interval from -2 to -1, including -2 but not including -1.