1. You have that the length of the yard is 10 feet more than 3 times the width. Then, you can write the following expression:
[tex]l=3w+10[/tex]
Where [tex]l[/tex] is the length and [tex]w[/tex] is the width.
2. She needs 60 feet of fencing, which is the perimeter.
3. The formula of the perimeter of a rectangle is:
[tex]P=2w+2l[/tex]
4. Therefore, you can substitute the first expression of the lenght into the formula of the perimeter and solve for the width:
[tex]60=2w+2(3w+10)\\60=2w+6w+20\\40=8w\\w=5[/tex]
5. Now you can calculate the length:
[tex]l=3(5)+10\\l=15+10\\l=25[/tex]
The answer is: The length of the yard is 25 feet.
