\[\boxed{\mathbf{515.}}\]
\[150 - 42\ :2 = 150 - 21 = 129\]
\[150 - 42 \cdot 2 = 150 - 84 = 66\]
\[150 - 42 + 2 = 108 + 2 = 110\]
\[300 - 14\ :2 = 300 - 7 = 293\]
\[300 - 14 \cdot 2 = 300 - 28 = 272\]
\[300 - 14 - 2 = 286 - 2 = 284\]
\[1000 - 400\ :5 = 1000 - 80 =\]
\[= 920\]
\[1000 - 400\ :8 = 1000 - 50 =\]
\[= 950\]
\[1000 - 400 - 5 = 600 - 5 =\]
\[= 595\]