Answer: x=10
Explanation:
By definition, if a line is parallel to one side of the triangle and intersects the other two sides in the samae ratio, then you can write the following ratio:
![AB/BC=AE/ED](https://img.qammunity.org/2020/formulas/mathematics/college/evwt9r8ru6m9dhww6s5t5g4rpsul40t4j7.png)
Now you must substitute values as followiing:
![25/15=(7x-40)/18\\(25/15)*18=7x-40\\30+40=7x\\x=10](https://img.qammunity.org/2020/formulas/mathematics/college/dk1n8ogf0rzz6qlh3ok5wcsqmt1djd3o6v.png)
Therefore, the answer is:
x=10