\[\boxed{\mathbf{203.}}\]
\[\textbf{а)}\ 360 + 20 = 380\]
\[450 - 40 = 410\]
\[280 - 200 = 80\]
\[510 - 1 = 509\]
\[130 + 60 = 190\]
\[940 - 20 = 920\]
\[\textbf{б)}\ 200 + 360 - 50 =\]
\[= 560 - 50 = 510\]
\[570 - 5 \cdot 6 = 570 - 30 = 540\]
\[740 - (89 - 69) = 740 - 20 =\]
\[= 720\]