Answer
$12$
Work Step by Step
The order of operations states that first we perform operations inside grouping symbols, such as parentheses, brackets, and fraction bars. Then, we simplify powers. Then, we multiply and divide from left to right. Finally, we add and subtract from left to right. We use these rules to simplify the expression.
Start with the expression: $3[42-2(10^2-9^2)]$
Since there are multiple layers of grouping, we must start by simplifying the innermost layer (the parentheses) in the order of operations:
First, we simplify the powers: $3[42-2(100-81)]$
We subtract inside parentheses: $3[42-2\times19]$
We now must simplify inside the brackets:
We multiply: $3[42-38]$
Next, we subtract: $3[4]$
Finally we multiply 3 by the number inside the brackets: $12$
