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