\[\boxed{\text{8\ (8).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ 2x - 3;\text{\ \ }\]
\[при\ x = 4;\ \ 0;\ - 3:\]
\[2 \cdot 4 - 3 = 8 - 3 = 5\]
\[2 \cdot 0 - 3 = - 3\]
\[2 \cdot ( - 3) - 3 = - 6 - 3 = - 9.\]
\[2)\ \frac{1}{3}a + \frac{1}{4}b;\]
\[при\ \ a = - 6;b = 16:\]
\[\frac{1}{3} \cdot ( - 6) + \frac{1}{4} \cdot 16 = - \frac{6}{3} + \frac{16}{4} =\]
\[= - 2 + 4 = 2.\]
\[3)\ 3m - 5n + 3k;\]
\[при\ \ m = - 7;n = 1,4;k = - 0,1:\]
\[3 \cdot ( - 7) - 5 \cdot 1,4 + 3 \cdot ( - 0,1) =\]
\[= - 21 - 7 - 0,3 = - 28,3.\]