\[17x - (2x + 5y) =\]
\[= 17x - 2x - 5y =\]
\[= 15x - 5y = 5 \cdot (3x - y)\]
\[3x - y = - 0,8:\]
\[5 \cdot (3x - y) = 5 \cdot ( - 0,8) = - 4.\]