\[\boxed{\mathbf{2.}\mathbf{99.ОК\ ГДЗ - домашка\ на\ }5}\]
\[\textbf{а)}\ 39\ 495 + 48\ 015 = 87\ 500\]
\[\textbf{б)}\ 9\ 000\ 284 + 1\ 678\ 678 =\]
\[= 10\ 678\ 962\]
\[\textbf{в)}\ 28\ 000\ 999\ 123 +\]
\[+ 39\ 789\ 001\ 789 =\]
\[= 67\ 790\ 000\ 912\]
\[\textbf{г)}\ 1\ 567\ 234\ 980 +\]
\[+ 8\ 432\ 765\ 107 =\]
\[= 10\ 000\ 000\ 087\]