Standard form is written Ax + By = C where A, B, and C are all integers.
In other words, no fractions.
Also, the A or the coefficient of the x term must be positive.
The only thing we need to do is add 7x to both sides to get 7x + y = -1.
So 7x + y = -1 is our answer.
If there are three sides and each side is 13 meters the do 13 times 3. Which equals 39 . Your answer is 39 m.