Pls solve this :-

Dear student,
we have, in general, for any two positive integers a and b,

$(-a)\times (-b)=a\times b$

Now,
$$\begin{gathered} (-31)\times (-100)=31\times 100=3100 \\ (-25)\times (-72)=25\times 72=1800 \\ (-83)\times (-28)=83\times 28=2324 \end{gathered}$$

Regards!