Answer:
2.25 hours
Explanation:
Let for x hours the total charges in school A and B are same,
For school A,
Fixed charges = $ 7,
Additional charges per hour = 20
Thus, the total charges for x hours = 7 + 20x
For school B,
Fixed charges = $ 25,
Additional charges per hour = $ 12,
Thus, the total charges for x hours = 25 + 12x
![\implies 7 + 20x = 25 + 12x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/nsugnszed7o0203yqks7h5jpowa52v3rdr.png)
![20x - 12x = 25 - 7](https://img.qammunity.org/2019/formulas/mathematics/middle-school/3nkmjfx2baf8d2lapcf20q1eof5g8jx707.png)
![8x = 18](https://img.qammunity.org/2019/formulas/mathematics/middle-school/coy865z379ifw3992z9ug7tfdt30yl4xas.png)
![\implies x = (18)/(8)=2.25\text{ hours}](https://img.qammunity.org/2019/formulas/mathematics/middle-school/6yspxiwtqvzumqoyf49ldv7dnazqya9nl4.png)