Hey there! I'm happy to help!
Let's create a basic rectangle with this length to width ratio.
Two sides are 3 and two of them have a length of 2. This would give us a perimeter (distance around) of 10.
We want to find a rectangle with a perimeter of 35 meters with this same ratio. What we can do is multiply all of the dimensions of our first rectangle by 3.5 (to get our perimeter of 10 to 35, we multiply by 3.5).
3×3.5=10.5
2×3.5=7
If we simplify 10.5:7, we have 3:2, and the perimeter of a rectangle with a length of 10.5 and a width of 7 would equal 35 meters.
Have a wonderful day! :D