How do you draw a picture of three sevens of a whole -in-one road

Step-by-step explanation:

Normally wiht number you would just have to do a rile of thirds, but in this case you need to used the values and to think a little outside the box.

YOu knwo that the total number of gallons is "n".

And the used gallons is "m"

To calculate the percentage used you use the next rule of three and clear for "x".

so that would be the expression for gallons used, the remaining gallons expression would be (n-m), so we do the same rule of three but witht the remaining gallons expression:

And that would be the expression for percentage of gallons left.