Here, we need to remember the signs rules
[tex]\begin{gathered} (+)(+\text{ )=+} \\ (+\text{ )(- )=-} \\ (-\text{ )(+ )=-} \\ (-\text{ )(- )=+} \end{gathered}[/tex]
Then
[tex](-4)+(-8)=-4-8=-12[/tex]
incorrect.
[tex](-9)-(-8)=-9+8=-1[/tex]
correct
[tex](+7)\times(-8)=-56[/tex]
correct
[tex](-5)(-2.5)=12.5[/tex]
correct
[tex]+\frac{1}{2}\times(+6)=3[/tex]
incorrect
