BODMAS RULE is used in simplification problems. The opertation are done in the following order in simplification.
B-->Bracket
D-->Division
M-->Multiplication
A-->Addition
S-->Subtraction
[tex]\begin{gathered} (10^2-8^2)\div(5+7)-6 \\ =(100-64)\div(12)-6\text{ (Did operations inside brackets)} \\ =36\div12-6\text{ } \\ =3-6\text{ (Did division 36 }\div\text{ 12)} \\ =-3 \end{gathered}[/tex]Therefore, the answer is -3.