\[\boxed{\mathbf{39\ (39)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[\mathrm{\Delta}ABC = \mathrm{\Delta}ABD = \mathrm{\Delta}BCD =\]
\[= \mathrm{\Delta}ACD\]
\[ABCD - тетраэдр.\]
\[\boxed{\mathbf{39}.}\]
\[1)\ 9a + 7a = 16a\]
\[2)\ 13y - 2y = 11y\]
\[3)\ 17k + k = 18k\]
\[4)\ 23x + 19x + 27x = 69x\]
\[5)\ 35x - x + 6 = 34x + 6\]
\[6)\ 16p + 4p - 9 = 20p - 9\]