math???calling all the math gorus

Question

anonymous · Answer

irenes gas tank was 9/10 full when  she left  her house and it was 7/15 full whaen she arrived

anonymous · Answer

what fraction of gas did she use driving

anonymous · Answer

$$\frac{ 3 }{ 3 }* \frac{ 9 }{ 10 }- \frac{ 7 }{ 15 }*\frac{ 2 }{ 2 }$$

anonymous · Answer

??? lost

solomonzelman · Answer

She has 9/10 of a full tank, and when she arrives to her house she has 7/15.
You have to subtract (9/10) from (7/15).

Do you understand why?

anonymous · Answer

na not rilly

solomonzelman · Answer

Lets do a different example, okay?

anonymous · Answer

wernin I suck at math no matter what grade

solomonzelman · Answer

Lets say you have 5 apples on your desk and you take a break to play outside. When you comeback you only have 2 apples.

How many apples dissapeared?

anonymous · Answer

3

solomonzelman · Answer

yes, and you did it by subtracting 5-2, right?

anonymous · Answer

k

anonymous · Answer

4tg battery low

solomonzelman · Answer

And here you are doing the same thing:

you have 9/10 of a gas tank, but then all (after driving to your house) you have (7/15)
(which is less than 9/10)

so, you have to subtract to find out how much gas was used up while driving.