一、计算题(共23分)
1. 口算。(5分)
$\frac{7}{12}+\frac{1}{12}=$
$2+\frac{1}{5}=$
$\frac{7}{8}+0.125=$
$\frac{1}{9}+\frac{1}{10}=$
$\frac{8}{15}+\frac{1}{5}=$
$\frac{7}{12}-\frac{1}{12}=$
$2-\frac{1}{5}=$
$\frac{7}{8}-0.125=$
$\frac{1}{9}-\frac{1}{10}=$
$\frac{8}{15}-\frac{1}{5}=$

1. $\frac{2}{3}$；$2\frac{1}{5}$；1；$\frac{19}{90}$；$\frac{11}{15}$；$\frac{1}{2}$；$1\frac{4}{5}$；$\frac{3}{4}$；$\frac{1}{90}$；$\frac{1}{3}$

2. 解方程。（6分）
$x-\frac{5}{6}=\frac{1}{9}$
$\frac{2}{7}+x=\frac{3}{4}$
$1.75x+\frac{1}{4}x=3$

2. $x=\frac{17}{18}$；$x=\frac{13}{28}$；$x=\frac{3}{2}$

3. 用递等式计算,能简算的要简算。(12分)
$\frac{1}{2}+\frac{3}{10}-\frac{1}{5}$
$\frac{9}{7}-\frac{5}{8}+\frac{3}{8}$
$1-12÷18-\frac{1}{3}$
$\frac{5}{12}-(0.3-\frac{1}{12})$
$\frac{7}{8}-0.2-\frac{3}{5}+0.125$
$\frac{5}{7}+\frac{2}{9}+(\frac{5}{7}-\frac{2}{9})$

3.
原式=$\frac{5}{10}+\frac{3}{10}-\frac{2}{10}=\frac{3}{5}$
原式=$\frac{9}{7}-(\frac{5}{8}-\frac{3}{8})=\frac{9}{7}-\frac{1}{4}=\frac{36}{28}-\frac{7}{28}=\frac{29}{28}$
原式=$1-\frac{2}{3}-\frac{1}{3}=1-(\frac{2}{3}+\frac{1}{3})=1-1=0$
原式=$\frac{5}{12}-0.3+\frac{1}{12}=\frac{5}{12}+\frac{1}{12}-0.3=0.5-0.3=0.2$
原式=$(\frac{7}{8}+\frac{1}{8})-(\frac{1}{5}+\frac{3}{5})=1-\frac{4}{5}=\frac{1}{5}$
原式=$(\frac{5}{7}+\frac{5}{7})+(\frac{2}{9}-\frac{2}{9})=\frac{10}{7}$