When Year 8 students look at algebraic expressions, they often make some common mistakes. These mistakes can make it hard for them to understand the math correctly. Let's look at some of these issues:

1. Getting the Order of Operations Wrong: Many students forget to follow the order of operations, which we remember with the letters PEMDAS (or BODMAS). For example, if they see the expression $3 + 2 \times (4 - 1)$, they might add $3 + 2$ first. This leads to the wrong answer! It’s important to remind students to always follow these steps in the right order.

2. Misusing Parentheses: Students often forget how to use parentheses correctly. They might see $2(x + 3)$ and think it means $2x + 3$, but it really means $2x + 6$. To fix this, we need to help them understand how to distribute and why parentheses are important.

3. Mixing Up Substituted Values: When it's time to substitute values into expressions, students can get confused and mix up the numbers or their signs. For example, if $x = -2$, evaluating $3x^2 + 4x$ could be done wrong. Teaching them to be careful and check their work can really help avoid this mistake.

4. Forgetting About Exponents: Sometimes, students don’t pay attention to exponents. They might think that $x^2$ means $2x$, but it actually means $x \times x$. If they practice more with different expressions, they will get better at remembering what exponents do.

By focusing on these common mistakes and practicing, students can get better at working with algebraic expressions.