Final answer:
The student made a mistake by not following the order of operations when evaluating the expression (30 = 6 - 1), which resulted in an incorrect answer.
Step-by-step explanation:
The student's error in calculating the value of the expression (30 = 6 - 1) lies in the incorrect application of order of operations. When solving mathematical expressions, order of operations must be followed, which means performing operations inside parentheses first, then exponents, followed by multiplication and division from left to right, and finally addition and subtraction from left to right. In this case, the student should first perform the subtraction inside the parentheses before applying any other operation.
For example, when we subtract 3 from 5, we calculate 5 - (+3) = 5 - 3 = 2. This means that we subtract the value 3, and its sign changes before operating addition. In a different scenario, when we subtract -6 from 2, the calculation will be 2 - (-6) = 2 + 6 = 8. This demonstrates how the subtraction of a negative number turns into addition.