When learning about variables and constants in Year 9 math, it’s easy to make some common mistakes. Here are a few I’ve seen that can really confuse students:

1. Confusing Variables and Constants:
   A variable, like $x$ or $y$, can change its value.
   A constant, like $3$ or $\pi$, stays the same.
   Remember this difference—variables change and can help you solve problems, while constants are like the strong base of a house.

2. Ignoring the Order of Operations:
   When you see something like $3 + 2x - 5$, don’t forget to use PEMDAS or BODMAS.
   Following the correct order helps you avoid mistakes when simplifying.

3. Misplacing Brackets:
   Brackets are very important!
   For example, $2(x + 3)$ is not the same as $2x + 3$.
   These two expressions will give you different answers, so always check to make sure you’ve used them properly!

4. Not Combining Like Terms:
   This is a major area where mistakes happen!
   When you simplify expressions, make sure to only combine like terms.
   For example, you can add $2x$ and $3x$ together, but leave constants like $5$ and $7$ separate to stay accurate.

5. Neglecting to Check Your Work:
   Always go back and check your steps and final answers.
   Even a small mistake can lead to a completely wrong answer.

By avoiding these common pitfalls, you’ll get better at understanding variables and constants in algebra. Happy calculating!