This exercise is about the hierarchy of operations (addition, subtraction, multiplication, and division). It goes as follows:
Comment: When you have consecutive operations of the same level, the operation on the left must be calculated first.
Now, after trying a little, we find that the correct distribution of parenthesis is
[tex]5^2-(0.2\cdot(8+12)\cdot\frac{1}{2})=25-(0.2\cdot20\cdot\frac{1}{2})=25-2=23.[/tex]Answer[tex]5^2-(0.2\cdot(8+12)\cdot\frac{1}{2})\text{.}[/tex]
