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第25頁

信息發(fā)布者：

$\frac{8}{7}$

$\frac{1}{4}$

$\frac{8}{15}$

$\frac{5}{66}$

$3\frac{4}{9}$

$3$

$\frac{5}{4}$

$\frac{4}{5}$

 $\begin{aligned}&\frac{5}{8}-\frac{3}{10}+\frac{2}{5}\\=&\frac{25}{40}-\frac{12}{40}+\frac{16}{40}\\=&\frac{25 - 12+16}{40}\\=&\frac{29}{40}\end{aligned}$

 $\begin{aligned}&\frac{5}{12}+\frac{4}{7}+(\frac{7}{12}+\frac{3}{7})\\=&(\frac{5}{12}+\frac{7}{12})+(\frac{4}{7}+\frac{3}{7})\\=&1 + 1\\=&2\end{aligned}$

 $\begin{aligned}&\frac{3}{10}+(\frac{3}{4}-\frac{3}{5})\\=&\frac{3}{10}+(\frac{15}{20}-\frac{12}{20})\\=&\frac{3}{10}+\frac{3}{20}\\=&\frac{6}{20}+\frac{3}{20}\\=&\frac{9}{20}\end{aligned}$

 $\begin{aligned}&\frac{7}{2}-\frac{4}{3}-\frac{5}{3}\\=&\frac{7}{2}-(\frac{4}{3}+\frac{5}{3})\\=&\frac{7}{2}-3\\=&\frac{7}{2}-\frac{6}{2}\\=&\frac{1}{2}\end{aligned}$

解:

 $\begin{aligned}x-\frac{3}{8}&=\frac{7}{6}\\x&=\frac{7}{6}+\frac{3}{8}\\x&=\frac{28}{24}+\frac{9}{24}\\x&=\frac{37}{24}\end{aligned}$

解:

 $\begin{aligned}1.6x + 0.5x&=8.4\\2.1x&=8.4\\x&=8.4\div2.1\\x&=4\end{aligned}$

解:

 $\begin{aligned}4x\times3&=9.6\\12x&=9.6\\x&=9.6\div12\\x&=0.8\end{aligned}$

C

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第25頁