1. 口算。
$\boldsymbol{\frac{1}{4}+\frac{3}{8}=}$
$\boldsymbol{\frac{1}{2}+\frac{3}{4}=}$
$\boldsymbol{\frac{2}{3}-\frac{1}{6}=}$
$\boldsymbol{\frac{5}{7}+\frac{1}{5}+\frac{2}{7}=}$
$\boldsymbol{\frac{2}{13}+\frac{5}{9}+\frac{11}{13}=}$
$\boldsymbol{\frac{4}{7}-\frac{5}{11}+\frac{3}{7}=}$

$\boldsymbol{\frac{5}{8}}$
$\boldsymbol{\frac{5}{4}} $
$\boldsymbol{\frac{1}{2}}$
$\boldsymbol{\frac{6}{5}} $
$\boldsymbol{\frac{14}{9}} $
$\boldsymbol{\frac{6}{11}}$

2. 计算。
$\boldsymbol{\frac{3}{4}+\frac{3}{8}+\frac{1}{2}}$
$\boldsymbol{\frac{3}{8}+\frac{4}{9}+\frac{1}{4}}$
$\boldsymbol{\frac{3}{4}+\frac{5}{7}+\frac{5}{8}}$
$\boldsymbol{\frac{5}{9}+\frac{3}{8}+\frac{1}{2}}$
$\boldsymbol{1-\frac{3}{10}-\frac{2}{5}}$
$\boldsymbol{\frac{23}{24}-\frac{1}{6}-\frac{3}{8}}$
$\boldsymbol{\frac{14}{15}-\frac{13}{15}+\frac{8}{15}}$
$\boldsymbol{6-\frac{6}{7}-\frac{5}{7}}$
$\boldsymbol{\frac{4}{5}-\frac{3}{10}+\frac{1}{5}}$

$\begin{aligned}\frac{3}{4}+\frac{3}{8}+\frac{1}{2}&=\frac{6}{8}+\frac{3}{8}+\frac{4}{8}\\&=\frac{13}{8}\end{aligned}$
$\begin{aligned}\frac{3}{8}+\frac{4}{9}+\frac{1}{4}&=\frac{27}{72}+\frac{32}{72}+\frac{18}{72}\\&=\frac{77}{72}\end{aligned}$
$\begin{aligned}\frac{3}{4}+\frac{5}{7}+\frac{5}{8}&=\frac{42}{56}+\frac{40}{56}+\frac{35}{56}\\&=\frac{117}{56}\end{aligned}$
$\begin{aligned}\frac{5}{9}+\frac{3}{8}+\frac{1}{2}&=\frac{40}{72}+\frac{27}{72}+\frac{36}{72}\\&=\frac{103}{72}\end{aligned}$
$\begin{aligned}1-\frac{3}{10}-\frac{2}{5}&=1-\frac{3}{10}-\frac{4}{10}\\&=\frac{3}{10}\end{aligned}$
$\begin{aligned}\frac{23}{24}-\frac{1}{6}-\frac{3}{8}&=\frac{23}{24}-\frac{4}{24}-\frac{9}{24}\\&=\frac{10}{24}\\&=\frac{5}{12}\end{aligned}$
$\begin{aligned}\frac{14}{15}-\frac{13}{15}+\frac{8}{15}&=\frac{9}{15}\\&=\frac{3}{5}\end{aligned}$
$\begin{aligned}6-\frac{6}{7}-\frac{5}{7}&=6-(\frac{6}{7}+\frac{5}{7})\\&=6-\frac{11}{7}\\&=\frac{31}{7}\end{aligned}$
$\begin{aligned}\frac{4}{5}-\frac{3}{10}+\frac{1}{5}&=\frac{4}{5}+\frac{1}{5}-\frac{3}{10}\\&=1-\frac{3}{10}\\&=\frac{7}{10}\end{aligned}$