♥ $$\times$$ ☺ $$=$$ ♦  ☺ is an even number.  Which of the following gives an odd answer? 
Overseas Competition->Knowledge Point->Number Theory Modules->Odd and Even Numbers->Multiplication Rules of Odd and Even Numbers
♥ $$\times$$ ☺ $$=$$ ♦  Since ☺ is an even number,~♦ must also be an even number.  ♦ $$-\textasciitilde7$$ is the only option to given an odd answer because even $$-$$ odd $$=$$ odd. 