Given the general rule for multiplication with signs:
[tex]\begin{gathered} (-)(-)=+ \\ (-)(\text{ + )=-} \\ (\text{ +)(-)=-} \\ (\text{ +)( +)=+} \end{gathered}[/tex]in this case, we have the following:
[tex](2)(-4)=-8[/tex]notice that we used the third case of the rule of the signs. Therefore, the answer is -8