\[\boxed{\mathbf{1304}\mathbf{\ (893)}.\ Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ (2,45 + 0,276) + 4,55 =\]
\[= (2,45 + 4,55) + 0,276 =\]
\[= 7 + 0,276 = 7,276\]
\[2)\ (9,37 + 13,6) + 6,4 =\]
\[= 9,37 + (13,6 + 6,4) =\]
\[= 9,37 + 20 = 29,37\]
\[3)\ 5,12 + 3,75 + 5,25 + 4,88 =\]
\[= (5,12 + 4,88) + (3,75 + 5,25) =\]
\[= 10 + 9 = 19\]
\[= 1 + 1 = 2\]