1 想一想，填一填。
(1) $\frac{3}{8} + \frac{5}{8} =?$

$\frac{3}{8} + \frac{5}{8} = \frac{(\ \ ) + (\ \ )}{(\ \ )} = \frac{(\ \ )}{(\ \ )} = (\ \ )$
(2) $1 - \frac{3}{16} =?$

$1 - \frac{3}{16} = \frac{(\ \ )}{(\ \ )} - \frac{3}{16} = \frac{(\ \ ) - (\ \ )}{(\ \ )} = \frac{(\ \ )}{(\ \ )}$
(3) $1 - \frac{7}{12} =?$
因为 $1 = \frac{(\ \ )}{(\ \ )}$，所以 $1 - \frac{7}{12} = \frac{(\ \ )}{(\ \ )} - \frac{7}{12} = \frac{(\ \ ) - (\ \ )}{(\ \ )} = \frac{(\ \ )}{(\ \ )}$。

(1)
$\frac{3}{8}+\frac{5}{8}=\frac{(3)+(5)}{(8)}=\frac{(8)}{(8)}=(1)$
(2)
$1-\frac{3}{16}=\frac{(16)}{(16)}-\frac{3}{16}=\frac{(16)-(3)}{(16)}=\frac{(13)}{(16)}$
(3)
因为 $1=\frac{(12)}{(12)}$，所以 $1-\frac{7}{12}=\frac{(12)}{(12)}-\frac{7}{12}=\frac{(12)-(7)}{(12)}=\frac{(5)}{(12)}$。

2 计算。
(1) $\frac{7}{17} + \frac{10}{17} =$
(2) $1 - \frac{1}{12} =$
(3) $\frac{(\quad)}{14} + \frac{6}{14} = 1$
(4) $1 - \frac{(\quad)}{(\quad)} = \frac{4}{7}$
(5) $\frac{5}{18} + \frac{2}{18} + \frac{(\quad)}{18} = 1$
(6) $\frac{2}{9} + \frac{7}{9} - 1 =$

(1)
$\frac{7}{17}+\frac{10}{17}=\frac{7+10}{17}=1$
(2)
$1-\frac{1}{12}=\frac{12}{12}-\frac{1}{12}=\frac{11}{12}$
(3)
$\frac{(8)}{14}+\frac{6}{14}=1$
(4)
$1-\frac{(3)}{(7)}=\frac{4}{7}$
(5)
$\frac{5}{18}+\frac{2}{18}+\frac{(11)}{18}=1$
(6)
$\frac{2}{9}+\frac{7}{9}-1=\frac{9}{9}-1=0$