Identify the expressions that contain variables.
a. `x+5`
b. `6-7`
c. `x-6y`
d. `2x`
e. -2
f. `6-3a `

Answer

To identify the expressions that contain variables, we will analyze each expression given in the question. A variable is typically represented by a letter (like x, y, or a) that can take on different values, while a numerical expression contains only numbers.

Let's go through the expressions step by step:

1. **Expression: `x + 5`**
- Here, `x` is a variable.
- Therefore, this expression contains a variable.

2. **Expression: `6 - 7`**
- This expression consists only of numbers.
- Therefore, it does not contain any variables.

3. **Expression: `x - 6y`**
- In this expression, both `x` and `y` are variables.
- Therefore, this expression contains variables.

4. **Expression: `2x`**
- Here, `x` is a variable.
- Therefore, this expression contains a variable.

5. **Expression: `-2`**
- This is just a numerical value.
- Therefore, it does not contain any variables.

6. **Expression: `6 - 3a`**
- In this expression, `a` is a variable.
- Therefore, this expression contains a variable.

### Summary of Expressions Containing Variables:
- The expressions that contain variables are:
- `x + 5`
- `x - 6y`
- `2x`
- `6 - 3a`