\[\boxed{\mathbf{163.}}\]
\[\textbf{а)}\ 560 - 500 = 60\]
\[100 + 280 = 380\]
\[402 - 2 = 400\]
\[713 - 13 = 700\]
\[30 + 400 = 430\]
\[600 - 1 = 599\]
\[\textbf{б)}\ 923 - 3 - 1 = 920 - 1 = 919\]
\[800 - 1 - 99 = 799 - 99 = 700\]
\[761 - 60 + 20 = 701 + 20 =\]
\[= 721\]