\[\boxed{\mathbf{109.}}\]
\[300 + 40 = 340\]
\[510 - 10 = 500\]
\[620 - 600 = 20\]
\[743 - 3 = 740\]
\[403 - 3 = 400\]
\[200 + 6 = 206\]
\[705 - 5 = 700\]
\[425 - 20 = 405\]
\[700 + 1 = 701\]
\[540 - 1 = 539\]
\[1000 - 100 = 900\]
\[1000 - 1 = 999\]