\[Стр.\ 70.\]
\[\boxed{\mathbf{10.}}\]
\[\textbf{а)}\ 42,56 - 17,798 + 20,7 =\]
\[= 63,26 - 17,\ 798 = 45,462\]
\[\textbf{б)}\ (3,07 + 4,78) - 2,09 =\]
\[= 7,85 - 2,09 =\]
\[= 5,\ 76\]
\[\textbf{в)}\ 34,978 - 21,4059 + 764,3 =\]
\[= 799,278 - 21,4059 =\]
\[= 777,8721\]
\[\textbf{г)}\ 30,06 - (7,085 + 8,02) =\]
\[= 30,06 - 15,105 = 14,955\]