Final answer:
The expression 7x[(9+8)-(12-7)] simplifies to 84. We solve inside the brackets first, then multiply by 7. Checking the result shows it to be a reasonable number given the small sizes of 7 and 12.
Step-by-step explanation:
To simplify the expression 7x[(9+8)-(12-7)], we first need to solve the operations within the brackets, which are also known as parentheses. Start by adding and subtracting the numbers inside the brackets:
- (9 + 8) gives us 17.
- (12 - 7) gives us 5.
Next, subtract the result of the second operation from the first:
17 - 5 equals 12.
Now, multiply this result by the number outside the brackets:
7x × 12 equals 84.
To check if the answer is reasonable, consider the magnitude of the numbers involved. Since 7 and 12 are relatively small and easy to perform in my head, it's reasonable to expect a result that isn't too large or small.