\[\boxed{\mathbf{779\ (779)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[\textbf{а)}\ ( + 7) \bullet ( - 4) = 7 \bullet ( - 4) = - 28\]
\[\textbf{б)}\ ( - 20) \bullet ( + 5) = ( - 20) \bullet 5 = - 100\]
\[\textbf{в)}\ ( + 15) \bullet ( - 3) = 15 \bullet ( - 3) = - 45\]
\[\textbf{г)}\ ( - 10) \bullet ( + 100) = ( - 10) \bullet 100 = - 1000\]
\[\textbf{д)}\ ( + 12) \bullet ( - 5) = 12 \bullet ( - 5) = - 60\]
\[\textbf{е)}\ ( - 1) \bullet ( + 32) = ( - 1) \bullet 32 = - 32\]