1. The given expression is 2 + 3(10 - 4).
2. The first step should be to solve the expression inside the parentheses: 10 - 4 = 6.
3. So, the expression becomes 2 + 3(6).
4. The error made here is that addition was done before multiplication. According to the order of operations, multiplication should be done before addition.
5. The correct next step is to multiply 3 by 6: 3 * 6 = 18.
6. Now, the expression becomes 2 + 18.
7. Finally, add 2 and 18: 2 + 18 = 20. The correct answer is 20, not 30. The error made was performing addition before multiplication, which goes against the order of operations.