Hot issues：
This module collects the frequently encountered and difficult problems for reference only.
This module collects the frequently encountered and difficult problems for reference only.
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一个分数是$\frac {13}{27}$，分子加上$x$，分母减去$x$，变化后的分子、分母在同时除以一个数后等于$\frac{45}{3}$，$x$是多少$？$
原来的分数为$\frac{13}{27}$
因为变化后的分子、分母同时除以一个数，最终数值不变，所以有： \begin{align} \frac {13+x}{27-x}=&\frac {45}3\\ =&15\\ =>\ \ 13+x=&405-15x\\ =>\ \ 16x=&392\\ =>\ \ x=&24.5 \end{align} 即，所求的$x$的值为：$x=24.5$